This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

U.S. President Joe Biden plans to travel to Brussels next week to meet with NATO allies about bolstering support for Ukraine as it fights to fend off Russia's unprovoked attack.

The "extraordinary summit" on March 24 will bring together North American and European leaders to discuss "further strengthening NATO's deterrence & defence," NATO Secretary-General Jens Stoltenberg said.

The alliance is expected to call on its military commanders Wednesday to send more troops and missile defenses to eastern Europe, Reuters reported. Ukraine President Volodymyr Zelenskyy is also scheduled to address U.S. lawmakers Wednesday morning.

Russia military 'struggling' to conduct operations as losses mount

Russia is transferring troops to Ukraine from as far away as its Pacific Fleet and is recruiting more mercenaries as it tries to replace lost personnel, according to an assessment from the U.K. Defence Ministry.

"As a result of these losses, it is likely Russia is struggling to conduct offensive operations in the face of sustained Ukrainian resistance," the ministry said. "Continued personnel losses will also make it difficult for Russia to secure occupied territory."

Russia's foreign ministry did not immediately respond to a request for comment.

It is unclear how many Russian soldiers have been killed in Ukraine since the invasion began in late February. Ukraine officials said over the weekend that Ukraine has lost 1,300 soldiers.

Moscow is redeploying troops from as far away as Armenia, its Eastern Military District, and the Russian Pacific Fleet, the ministry said.

The Pacific Fleet is based in Vladivostok, Russia. By air, Vladivostok is more than 4,400 miles (7,100 km) from Kyiv.

The U.K. Defence Ministry said Russia is seeking mercenaries from Syria and "private military companies," the term used to describe Russia-based firms that hire out armed fighters.

Moscow will likely use those mercenaries to hold seized Ukrainian territory so it can shift more of its regular troops to fight Ukrainian troops and "renew stalled offensive operations," the U.K. ministry said.

Russian corporate fighters have been accused of committing human rights abuses in Syria, Libya and the Central African Republic while working on behalf of Moscow.

Such mercenary services already operated in eastern Ukraine prior to Russia's current invasion, according to the U.S. government.

In 2017, the U.S. Treasury placed sanctions on the biggest Russian mercenary company, PMC Wagner, and its founder, Dmitriy Utkin, for "actions or policies that threaten the peace, security, stability, sovereignty, or territorial integrity of Ukraine."

The Washington-based Center for Strategic and International Studies said last year that Moscow provided security and military services through private mercenary companies to the government of the Central African Republic in exchange for the right to extract gold, uranium and diamonds.

— Ted Kemp

Surveying the damage from a rocket attack in Kharkiv

First responders work in a building that was struck by a Grad rocket attack in Kharkiv.

-Adam Jeffery

NATO to begin planning for more troops on eastern flank

NATO is set to tell its military commanders on Wednesday to draw up plans for new ways to deter Russia following Moscow's invasion of Ukraine, including more troops and missile defenses in eastern Europe, officials and diplomats said.

Defense ministers will order the military advice at NATO headquarters, just over a week before allied leaders, including U.S. President Joe Biden, gather in Brussels on March 24.

Ministers will also hear from their Ukrainian counterpart Oleksii Reznikov, who is expected to plead for more weapons from individual NATO countries, as Russian attacks on Ukraine's cities continue and the Russian military seeks control of Kyiv.

"We need to reset our military posture for this new reality," NATO Secretary General Jens Stoltenberg said earlier Tuesday. "Ministers will start an important discussion on concrete measures to reinforce our security for the longer term, in all domains," he told reporters.

— Reuters

Ukrainian journalist working for Fox News dies while on assignment

A second journalist on assignment for Fox News in Ukraine has died, the television news network confirmed.

Oleksandra Kuvshynova, affectionately called Sasha, died alongside cameraman Pierre Zakrzewski after their vehicle was struck by incoming fire on Monday.

The confirmation of Kuvshynova's death follows that of Zakrzewski.

"Sasha was just 24 years old and was serving as a consultant for us in Ukraine. She was helping our crews navigate Kyiv and the surrounding area while gathering information and speaking to sources. She was incredibly talented and spent weeks working directly with our entire team there, operating around the clock to make sure the world knew what was happening in her country," CEO Suzanne Scott wrote in a statement.

"Her dream was to connect people around the world and tell their stories and she fulfilled that through her journalism," Scott wrote.

— Amanda Macias

State Department says Russia isn't negotiating in good faith

The State Department said the U.S. is prepared to engage with Russia on ending the war in Ukraine, but Moscow has yet to take negotiations seriously.

"We have yet to find a Russian interlocutor that is either able or willing to negotiate in good faith and certainly not in the context of de-escalation," State Department spokesman Ned Price said.

"A number of our partners are engaged directly with the Russian Federation at high levels. I think what is clear is that none of these engagements have yet resulted in a diminution of violence or in a reduction of the loss of life that we've seen across Ukraine," Price added.

President Joe Biden last spoke to Russian President Vladimir Putin on Feb. 12., nearly two weeks before Russian troops began their invasion of Ukraine.

— Amanda Macias

Russia has launched more than 950 missiles into Ukraine

Russian forces have launched more than 950 missiles since the start of the Ukraine invasion, a senior U.S. Defense official said, adding that the Pentagon has observed a steady rise in missile launches amid stalled ground movements.

The official, speaking on the condition of anonymity, said the Russian arsenal includes short-range, medium-range, ballistic and cruise missiles.

The official said "Kyiv remains under bombardment by long-range fires" and targets include residential areas. The official said Russian forces have not appreciably advanced on Kyiv and are approximately 10 miles northwest of the capital and about 13 miles to the east.

— Amanda Macias

U.S. lobbyists connect Ukraine officials with powerful allies to help in war against Russia

Lobbyists are working to connect Ukrainian officials with powerful allies in the U.S., including mayors, governors and representatives of at least one firearms dealer, in an effort to help the war-torn country in its fight against Russia.

At least one U.S. firm and a separate lawyer each recently disclosed to the Department of Justice's Foreign Agents Registration Act unit that they started pro-bono work for Ukrainian government officials since the start of Russia's invasion. These advisors have started to help Ukrainian leaders as Western sanctions have led lobbyists to distance themselves from Russian-backed entities. The powerful lobbying firm Sidley Austin dropped VTB Bank as a client after the Biden administration sanctioned the financial institution.

Your Global Strategy, a lobbying and communications firm co-founded by international political strategists Shai Franklin and Michael Steiner, is working to connect local Ukrainian government officials with American mayors and governors, Franklin told CNBC in an interview on Tuesday. He later noted that he is the sole lobbyist from Your Global Strategy working on this effort.

Steiner previously worked closely with Russia as the Moscow-Russia CEO for the American Jewish Joint Distribution Committee, winning a special citation from the Russian Federation for "contributions to the development of nationalities," according to his bio.

— Brian Schwartz

Large Russian convoy heading for Kyiv is stalled, Pentagon says

A large Russian military convoy, widely tracked by satellite imagery, appears to have made little progress for nearly a week, according to U.S. military estimates.

"We have no updates on the convoy. It is still stuck," a senior U.S. Defense official, who spoke on the condition of anonymity, told reporters Tuesday when asked about the latest satellite imagery provided by Maxar Technologies.

Last week, the official told reporters that "the convoy is not really going anywhere" and that it was not immediately clear how many vehicles are in the Russian convoy.

— Amanda Macias

'That is just the beginning': White House says more Russian yachts and assets set to be seized

White House press secretary Jen Psaki had a strong warning for Russian oligarchs: the United States and its Western allies are not done seizing their yachts.

"That is just the beginning," Psaki said after she confirmed U.S. allies had seized a number of yachts around the world.

President Joe Biden's administration recently announced a taskforce that would seek to deprive Russian oligarchs of assets and other tools used to evade sanctions following their country's invasion of Ukraine.

Psaki confirmed that five additional yachts owned by Russia's wealthiest executives have been seized by authorities, including a nearly 300-foot superyacht owned by Sergey Chemezov. Psaki said the yacht was seized in Spain. Chemezov, the CEO of Russian conglomerate Rostec, was sanctioned by Biden's administration.

The yacht is named Valerie and is worth about $100 million, according to Superyacht Fan.

— Brian Schwartz

Biden will head to Brussels for NATO summit

U.S. President Joe Biden will travel to Brussels for a March 24 NATO summit about how to respond to Russia's invasion of Ukraine, the White House said.

White House press secretary Jen Psaki told reporters Biden will discuss "ongoing deterrence and defense efforts in response to Russia's unprovoked and unjustified attack on Ukraine, as well as to reaffirm our ironclad commitment to our NATO allies."

NATO Secretary-General Jens Stoltenberg announced what he called an "extraordinary" meeting earlier in the day.

"We will address #Russia's invasion of #Ukraine, our strong support for Ukraine, and further strengthening NATO's deterrence & defence," Stoltenberg wrote in a tweet. "At this critical time, North America & Europe must continue to stand together."

— Jacob Pramuk

White House press secretary holds briefing on Ukraine, Covid

Fox News cameraman killed while working in Ukraine

Pierre Zakrzewski, a cameraman for Fox News, was killed on Monday while reporting from Ukraine, Fox News CEO Suzanne Scott announced to employees in a memo.

"It is with great sadness and a heavy heart that we share the news this morning regarding our beloved cameraman Pierre Zakrzewski. Pierre was killed in Horenka, outside of Kyiv, Ukraine. Pierre was with Benjamin Hall yesterday newsgathering when their vehicle was struck by incoming fire," Scott wrote.

Scott wrote that Zakrzewski, a long-time war zone photographer with dispatches from Iraq and Syria, traveled to Ukraine in February. She said he had "vast" talents and "did it all under immense pressure."

Scott offered condolences to Zakrzewski's family and noted that Benjamin Hall, a Fox correspondent injured in Ukraine, remains hospitalized.

On Sunday, award-winning American filmmaker and journalist Brett Renaud was killed in Ukraine, the first U.S. reporter to die in the conflict.

— Amanda Macias

U.S. imposes sanctions on Russians over human rights violations

The United States imposed sanctions on Russians it accused of gross human rights violations and slapped fresh measures on Belarus President Alexander Lukashenko, increasing pressure on Moscow and its close ally amid the war in Ukraine.

The U.S. Treasury Department said it was imposing sanctions on four people and one entity it accused of playing a role in concealing events around the death of whistleblower Sergei Magnitsky or of being connected to human rights violations against human rights advocate Oyub Titiev.

The Treasury statement also said it was adding to its sanctions against Lukashenko and also targeting his wife.

— Reuters

Russia bars Clinton, Biden, Blinken and others

Russia said has barred U.S. President Joe Biden, Secretary of State Antony Blinken and other top officials from entering the country.

Former Secretary of State Hillary Clinton was also named to Russia's "stop list" along with Defense Secretary Lloyd Austin, CIA chief William Burns and National Security Adviser Jake Sullivan. They were included on a list of 13 individuals banned from Russia in response to sanctions imposed by Washington on Russian officials.

But the foreign ministry said it was maintaining official relations with Washington and if necessary would make sure that high-level contacts with the people on the list could take place.

— Reuters

NATO has no plans to deploy nuclear-capable weapons systems amid Russia threat, Stoltenberg says

NATO Secretary-General Jens Stoltenberg said the 30-member military alliance has no plans to shift mobile nuclear-capable weapons systems closer to Russia's borders, disputing a previous claim by Moscow.

In February, Russian President Vladimir Putin placed his nation's nuclear forces on high alert amid tensions with the West over his invasion of Ukraine. At the time, Putin said he ordered the elevation because of "aggressive statements" made against Russia by NATO.

"We have no plans to deploy nuclear-capable intermediate-range land-based systems in Europe," Stoltenberg said ahead of a two-day NATO defense ministers meeting.

"At the same time, we need to be able to make sure that we are able to respond and protect all allies in the new security environment where Russia has deployed more nuclear-capable missiles," he said, adding that the alliance would invest in "readiness and the ability to monitor and detect" missile threats.

"We also need to make sure that NATO's nuclear deterrence remains safe and secure and effective and that's exactly what we're doing," he added.

— Amanda Macias

Russian missile strikes residential building in Kharkiv

Rescuers remove debris from a residential building damaged by an airstrike in the city of Kharkiv, as Russia's attack on Ukraine continues.

— Adam Jeffery

NATO chief Stoltenberg says he is concerned Russia is weighing chemical weapons use

NATO is increasingly concerned that Russian President Vladimir Putin is considering the use of chemical weapons in his invasion of Ukraine, the alliance's Secretary-General Jens Stoltenberg said.

Stoltenberg said that the Kremlin has started to spread false propaganda that Ukraine and its allies are developing chemical weapons, leading the NATO chief to worry whether Putin himself is weighing the use of the illegal munitions.

"Any use of chemical weapons will be a violation of international law," Stoltenberg said at a news conference from NATO headquarters in Brussels. "We are concerned Moscow could stage a false flag operation in Ukraine, possibly with chemical weapons."

— Thomas Franck

Biden slated to authorize $13.6 billion in aid for Ukraine

President Joe Biden is slated to sign into law a massive $1.5 trillion omnibus spending package that contains aid for Ukraine.

The 2,741-page bipartisan appropriation measure, known as H.R. 2471 or the Consolidated Appropriations Act, also includes $13.6 billion in military and humanitarian aid for Ukraine.

"We will make sure Ukraine has weapons to defend against the invading Russian force. We will send money and food and aid to save Ukrainian lives. We will welcome Ukrainian refugees with open arms," Biden said via Twitter.

— Amanda Macias

NATO Secretary General Stoltenberg holds briefing on Ukraine crisis

'This is not a time for countries to sit on the sidelines,' U.S. Ambassador to NATO says

President Joe Biden's ambassador to NATO called on all countries to make clear where they stand amid the ongoing conflict in Ukraine.

"This is not a time for countries to sit on the sidelines. This is not a time for countries to pretend like they could stay neutral on this particular conflict," U.S. Ambassador to NATO Julianne Smith said on a call with reporters.

Smith's comments follow an intense seven-hour meeting between U.S. and Chinese officials in Rome on Monday. The U.S. delegation, led by national security adviser Jake Sullivan, conveyed to Beijing's top diplomat, Yang Jiechi, that China should not assist Russia amid the Kremlin's ongoing war in Ukraine.

"The goal of that engagement was to really send a pretty clear message that the United States is keen to see every country around the world and that includes the PRC to make clear in this moment where they stand with respect to this conflict in Ukraine," Smith said, referring to the People's Republic of China.

"And that they need to stand on the side of the rules-based order," she added.

— Amanda Macias

Russia-Ukraine talks resume

Mykhailo Podolyak, an advisor to Ukrainian President Volodymyr Zelenskyy and a participant in talks with Russian officials, has said negotiations are continuing after a fourth round on Monday.

— Chloe Taylor

U.S. Defense Secretary Austin heads to NATO meeting

U.S. Defense Secretary Lloyd Austin will travel to Belgium for an in-person meeting of NATO defense ministers as the alliance looks to bolster Ukraine in its effort to fight off Russia's invasion.

Following the two-day gathering in Brussels, Austin will travel to NATO member states Slovakia and Bulgaria.

"We're thrilled to welcome back the secretary this evening and have him here tomorrow for two sessions. We'll cover the situation in Ukraine but we'll also be talking about some longer-term questions about how NATO should be positioning itself in the future," U.S. Ambassador to NATO Julianne Smith said on a call with reporters Tuesday.

— Amanda Macias

2,000 cars have left Mariupol, authorities say

Mariupol City Council has said 2,000 cars had left the city as of 2 p.m. local time on Tuesday.

A further 2,000 cars were "parked at the exit from the city," the authority said in a Telegram post.

Mariupol was one of several Ukrainian cities to have a humanitarian corridor opened on Tuesday for the evacuation of civilians and the import of vital supplies like water and medicine.

Hundreds of thousands of civilians have been trapped by heavy combat in the besieged city, the Red Cross said over the weekend. Early attempts to evacuate civilians from Mariupol had to be halted because Ukrainian authorities said Russian forces had violated cease-fire agreements in the city.

Mariupol is crucial in the war for Ukraine, as its capture could help Russian forces create a land corridor to Crimea — a peninsula in the country's south that Moscow invaded and annexed in 2014.

— Chloe Taylor

Kyiv mayor says 4 were killed in Russian airstrikes

Four people were killed in Russian missile strikes on Kyiv this morning, the city's Mayor Vitali Klitschko has said.

Several residential buildings were hit in the attacks on the Ukrainian capital, with high-rise apartment buildings catching fire after the strikes.

Klitschko said in a Telegram post on Tuesday afternoon that emergency services were still working to extinguish a fire in Kyiv's Sviatoshynskyi district hours after the attack.

"We will defend our city — we never think to leave. It's our home," he told reporters in a video posted to his Telegram account.

— Chloe Taylor

Giving birth during an air raid in Mykolaiv

Aleina gives birth to her baby in the basement of a maternity hospital as sirens warn for Russian air raids in Mykolaiv, Ukraine, on Monday. 

European finance ministers discuss response to Ukraine conflict

The finance ministers of France, Germany and the Netherlands have spoken to CNBC's Silvia Amaro about the EU's response to the Russian invasion of Ukraine, and the potential economic ramifications of European sanctions on Moscow.

— Chloe Taylor

Ukraine conflict creating 1 child refugee per second, U.N. charity says

The number of refugees who have fled Ukraine since the start of the war has reached 2.95 million, the U.N.'s human rights office said Tuesday.

It came as the U.N. children's charity UNICEF said more than 1.5 million children had become refugees since the conflict began 20 days ago — equating to one child refugee per second.

On average, more than 75,000 children were becoming refugees every day as the war in Ukraine raged on, the organization said.

"So long as this war continues, the situation for Ukraine's children will only get worse," UNICEF spokesperson James Elder said at a press briefing in Geneva, Switzerland.

— Chloe Taylor

UK, EU slap Moscow with barrage of fresh sanctions

The U.K. and the EU both revoked Russia's "most favored nation" trading status on Tuesday, paving the way for Russian goods to be subject to harsh import tariffs.

"Most-favored nation" status is a classification within the World Trade Organization that exempts a country from tariffs.

Britain's government said Tuesday that it would ban exports of high-end luxury goods to Russia, while hitting hundreds of imports from the country with new tariffs.

It published an initial list of Russian and Belarusian goods worth £900 million that would now be subject to an additional 35% import tariff on top of existing levies. Products on the list include vodka, fur, cement and several metals.

The move to ban the export of goods such as luxury vehicles, high-end fashion and works of art was a coordinated effort being undertaken by G-7 nations, and would come into force soon, the U.K. government said.

Meanwhile, EU lawmakers on Tuesday approved several new measures, including a ban on transactions with certain Russian state-owned businesses, a ban on Russian steel imports, a ban on new investments in Russia's energy sector and an export ban on luxury goods to Russia.

Banning imports of Russian steel to the EU would amount to 3.3 billion euros ($3.63 billion) in lost export revenue for Russia, the EU said.

— Chloe Taylor

Many killed in fresh attacks across Ukraine

Fresh bombings across Ukraine have led to multiple civilian deaths, Ukrainian authorities said Tuesday.

Vitalii Koval, head of the Rivne regional state administration, said on Telegram that 19 people had died following an airstrike on a television tower in the region yesterday, while a further nine had been wounded.

Meanwhile, the Ukrainian State Emergency Services said Tuesday that two people had died in Kyiv's Sviatoshyno district when a 16-storey residential building caught fire following a Russian shelling attack.

— Chloe Taylor

9 humanitarian corridors open in Ukraine

Nine humanitarian corridors have been opened in Ukraine to evacuate civilians from besieged towns and cities, the country's Deputy Prime Minister Iryna Vereshchuk announced Tuesday.

The safe routes will also allow the import of humanitarian aid, including tons of water and medicine.

Cities where evacuations are planned include Mariupol, Sumy, Trostyanets and three villages in the Kyiv region.

"We promise not to leave anyone behind," Vereshchuk said in a statement. "We remember, we know and we really want to save you."

Some evacuation attempts in recent weeks have had to be abandoned, with Ukrainian authorities saying Russian forces had violated cease-fire agreements and attacked the safe routes out of certain cities.

— Chloe Taylor

Kyiv prepares for 35-hour curfew

Mayor of Kyiv Vitaliy Klitschko has announced a 35-hour curfew in the Ukrainian capital starting Tuesday evening.

From 8 p.m. local time on Tuesday until 7 a.m. Thursday, Kyiv residents will be prohibited from moving through the city without a special pass, and will only be allowed to leave their homes to reach bomb shelters.

Klitschko said in a Telegram post Tuesday morning that the decision had been made by military command because the city had found itself in "a difficult and dangerous moment."

"I ask all Kyivites to prepare for the fact that they will have to be at home for two days or, in case of an alarm, in a shelter," he said.

— Chloe Taylor

Russia-Ukraine talks set to resume today

Talks between Russia and Ukraine are expected to continue Tuesday following a fourth round of negotiations yesterday.

Mykhailo Podolyak, an advisor to Ukrainian President Volodymyr Zelenskyy and a participant in the talks, said Monday that the negotiations had taken "a technical pause … until tomorrow."

He said a break was being taken to carry out "additional work in the working subgroups and clarification of individual definitions."

— Chloe Taylor

Poland, Slovenia and Czech Republic leaders heading to Kyiv

The prime ministers of Poland, Slovenia and the Czech Republic — all members of both NATO and the EU — will travel to Kyiv today to meet with Ukraine's president and prime minister.

Poland's deputy prime minister will also join the delegation.

Polish Prime Minister Mateusz Morawiecki and his Czech counterpart Petr Fiala both said in statements Monday morning that the visit had been organized in consultation with European Council President Charles Michel and European Commission President Ursula von der Leyen.

The U.N. had also been informed of the visit, they said.

"The purpose of the visit is to confirm the unequivocal support of the entire European Union for the sovereignty and independence of Ukraine," the statements added. "The aim of this visit is also to present a broad package of support for the Ukraine and Ukrainians."

— Chloe Taylor

Russia attempting to ‘subvert Ukrainian democracy,’ UK warns

"Reporting suggests that Russia may seek to stage a 'referendum' in Kherson in an attempt to legitimize the area as a 'breakaway republic' similar to Donetsk, Luhansk and Crimea," the U.K. Ministry of Defense said in an intelligence update on Tuesday.

Kherson, the first major Ukrainian city to be captured by forces after Russia launched its invasion, has been the scene of protests against Russian occupation in recent weeks. The U.K.'s intel update on Tuesday said that further protests were seen in the city yesterday, with Russian forces reportedly firing warning shots in an attempt to disperse peaceful protesters.

Elsewhere, Russia is reported to have installed its own mayor in the city of Melitopol, according to the U.K., following the reported abduction of the city's elected mayor on Friday. The U.K.'s update said the mayor of Dniprorudne is also thought to have been abducted by Russian forces.

"Russia is likely to make further attempts to subvert Ukrainian democracy as it attempts to consolidate political control of Ukraine," the British Ministry of Defense said.

— Chloe Taylor

Shells have hit several residential buildings, Kyiv mayor says

Mayor of Kyiv Vitaliy Klitschko has said shells hit several residential buildings in the Ukrainian capital early this morning.

Two high-rise buildings in Kyiv's Sviatoshyno district, one high-rise building in the Podil district, and a private house were hit by Russian ammunition, he said in a Telegram post.  

"The entrance to one of the metro stations was damaged by the shock wave," Klitschko added, according to an NBC News translation. "There are victims in residential buildings, the information is being clarified. Rescuers and medics are working on the ground."

— Chloe Taylor

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Russia-Ukraine talks done for the day; EU agrees to fresh sanctions