This has been CNBC's live blog covering updates on the war in Ukraine. [Follow the latest updates here.]

The United Nations and the International Committee of the Red Cross began evacuating civilians from the besieged southern port city of Mariupol, and the operation will continue on Monday.

"The Mariupol humanitarian operation will continue until we achieve our goals — saving the lives of our citizens," Iryna Vereshyuk, Ukraine's deputy prime minster, said in a message she posted on Telegram, according to an NBC News translation. Around 100 civilians have been rescued so far, Ukrainian President Volodymyr Zelenskyy said.

A few thousand civilians and Ukrainian fighters have been holed up in the sprawling Azovstal steel plant in Mariupol, and about 100,000 people still remain in Mariupol, officials have said.

Zelenskyy met with U.S. House Speaker Nancy Pelosi and a Congressional delegation in Kyiv. He called the U.S. a "leader in strong support" for Ukraine. The delegation praised the courage of the Ukrainian people during a visit to Poland. Pelosi vowed that Washington would stand with the country until it defeats Russia.

Jill Biden to meet with refugees in trip to Romania and Slovakia

First lady Jill Biden will travel to Romania and Slovakia this week, coming within miles of the Ukrainian border.

During her trip, Biden is expected to meet with U.S. service members, embassy staff, senior officials in Romania and Slovakia, humanitarian aid workers and refugees.

The first lady's trip follows other visits to the region by high-level U.S. officials, including Secretary of State Antony Blinken, Secretary of Defense Lloyd Austin and House Speaker Nancy Pelosi.

— Christine Wang

Nancy Pelosi reiterates U.S. support for Ukraine

House Speaker Nancy Pelosi said additional U.S. support for Ukraine is on the way following U.S. President Joe Biden's massive aid package proposal.

In a statement, Pelosi said the Congressional delegation met with Ukraine's President Volodymr Zelenskyy and "conveyed our respect and gratitude to President Zelenskyy for his leadership and our admiration of the Ukrainian people for their courage in the fight against Russia's diabolical invasion."

Pelosi also said the delegation went to Poland "to send an unmistakable message to the world: that America stands firmly with our NATO allies in our support for Ukraine."

She said the delegation will be meeting with Poland's President Andrzej Duda and other senior officials to discuss how they can further work together to support Ukraine.

— Christine Wang

4 civilians dead in Donetsk region, governor says

Four civilians were reported killed and 11 more were injured by Russian shelling in the Donetsk region on Sunday, the Ukrainian regional governor said that evening.

The deaths and seven of the injuries were in the northern city of Lyman, governor Pavlo Kyrylenko wrote in a Telegram post. One person also died in the city of Bakhmut from injuries received in the Luhansk region, he said.

In the same post, Kyrylenko said that it was impossible to determine the number of victims in the bombed-out port city of Mariupol and the town of Volnovakha, which is controlled by pro-Kremlin separatists.

— Associated Press

Russia's highest-ranking uniformed officer visited dangerous front lines to try and change the course of the flagging battle

Russia's highest-ranking uniformed officer, Gen. Valery Gerasimov, visited front-line positions in eastern Ukraine late last week, the New York Times reported. The chief of the general staff of Russia's military's dangerous move reportedly was meant to try and turn around the stalled effort to succeed in its offensive against resilient Ukrainian soldiers.

Ukrainian forces launched an attack at one of the locations Gerasimov visited in the Russian-controlled city of Izium after the general had already left to return to Russia, the Times reported. A Ukrainian official told the Times that that attack resulted in the death of 200 Russian soldiers, including at least one general.

Read the complete New York Times report here.

— Terri Cullen

Russia's Lavrov says May 9 not a relevant date for Ukraine operations

The upcoming anniversary of Russia's liberation at the end of World War II will have no bearing on Moscow's military operations in Ukraine, the country's foreign minister said on Italian television on Sunday.

"Our soldiers won't base their actions on a specific date," Sergei Lavrov said when asked whether the May 9 anniversary would mark a turning point in the conflict.

"We'll commemorate our victory in a solemn manner but the timing and speed of what is happening in Ukraine will hinge on the need to minimize risks for civilians and Russian soldiers," he added, speaking in Russian through an Italian interpreter.

— Reuters

Ukraine foreign minister urges EU to include Russian oil embargo in next sanctions

Ukraine's foreign minister pressed the European Union to include an embargo on Russian oil in its next round of proposed sanctions on Russia.

Future sanctions "must include an oil embargo," Dmytro Kuleba told the European Union's high representative of foreign affairs and security policy, Josep Borrell Fontelles, Kuleba wrote in a tweet.

The EU is already planning to propose a ban on Russian oil, Bloomberg News reported on Saturday. A ban would require approval from ambassadors representing all 27 EU countries, and the ambassadors will meet this week, Bloomberg said.

Kuleba said he told Borrell that "there can be no alternative to granting" Ukraine a status as a candidate for being admitted to the European Union. Kuleba also said he discussed the importance of a safe evacuation from the Ukrainian city of Mariupol.

— Catherine Clifford

Congressman Kinzinger introduces bill that would allow U.S. military to respond to Russian escalation

Republican congressman Adam Kinzinger from Illinois announced legislation that would allow the U.S. to respond to the Russian war in Ukraine with military force if Vladimir Putin "escalates his war," according to a statement.

The measure, named Authorization for Use of Military Force to Defend America's Allies Resolution of 2022, would, if passed, pave the way for the U.S. military to respond if Russia uses chemical, biological, or nuclear weapons against Ukraine.

"The targeting of civilians, mass executions, and countless reports of rape by Russian forces have gone largely unchecked. We must take action to put a stop to these atrocities. Words matter, but so do our actions," Kinzinger is quoted as saying in the statement. "I'm introducing this AUMF as a clear redline so the administration can take appropriate action should Russia use chemical, biological, and/or nuclear weapons. We must stand up for humanity and we must stand with our allies."

Also currently sitting in front of Congress is President Joe Biden's request for $33 billion in aid to Ukraine, which has gotten delayed by an ask for an additional $10 billion for Covid-19 relief funding. Earlier this week the House passed the Ukraine Democracy Defense Lend-Lease Act of 2022 after the legislation received Senate approval. President Biden's signature of the bill would allow the U.S. to lend or lease weapons to Ukraine.

— Catherine Clifford

Ukraine armed forces say they're holding back Russian troops

The Russian invasion of Ukraine failed in multiple locations, a representative for the Ukrainian military said.

Russian forces "tried to lead offensive actions" near Izium, a city on the Donets River in eastern Ukraine, but they "had no success" and "suffered losses in manpower and equipment," according to a Facebook post from the spokesman of the general staff of the Ukrainian armed forces, Alexander Štupun.

The Russian military forces also tried to take the settlements of Rubížne and Popasna, also in the eastern part of Ukraine, but they had "no success" and took losses, Štupun said. He said the Ukrainians withstood Russian attacks in Maryinka, Ozerne, Vremivka and Green Field, among others.

In other locations, where the Russians were unsuccessful in their efforts, they were gathering information about the Ukrainian position with aircraft, Štupun said.

Meanwhile, Russia is gathering troops in the south part of Ukraine to move on the Dnipropetrovsk region, according to a video posted on Telegram from Ukrainian President Volodymyr Zelenskyy. The movement "may be Russia's strategic success in the war," Zelenskyy said, according to an NBC News translation.

Zelenskyy reiterated Ukraine's resolve to fight.

"Honestly, I do not know — the lives of people destroyed, burned or stolen property will not do anything to Russia, but will increase the toxicity of the Russian state and the number of those in the world who will work to isolate Russia," Zelenskyy said. "The Armed Forces of Ukraine are responding to the aggressors with all their blows and will continue to respond until the occupiers leave our land."

— Catherine Clifford

Kharkiv leader warns residents to remain sheltered as fighting intensifies

Kharkiv residents in the northern and eastern districts of the city should stay in their shelters due to heavy Russian shelling, regional governor Oleh Synehubov said in a Telegram post.

Kharkiv, Ukraine's second largest city, has been faced with intermittent bombing since Russia began its full scale invasion in late February. But fighting around the city has intensified in recent days as Ukrainian troops have worked to push back Russian forces, according to the New York Times.

— Jessica Bursztynsky

Schumer details plan to liquidate assets of sanctioned Russian oligarchs

In a new push to increase sanctions against Russian oligarchs, Senate Majority Leader Chuck Schumer, D-N.Y., detailed a plan to liquidate billions in frozen assets and donate the proceeds to Ukraine.

Already, more than $30 billion in Russian assets has been frozen. However, under U.S. law and most laws in Europe, assets that are frozen remain under the ownership of the oligarch and can't be transferred or sold. 

Speaking at a press conference, Schumer said the U.S. should pass legislation to sell the seized yachts, helicopters, real estate, artwork and other property and funnel the proceeds to the Ukrainians.

"It's time for sanctioned Russian oligarchs to be held accountable for the ill-gotten wealth they have received and to give the money to the Ukrainian people and the Ukrainian government who desperately need it," he said.

Schumer said he intends to bring this push to a Senate vote, along with a $33 billion aid package to Ukraine. 

— Jessica Dickler

U.K. says it discovered 'sick' Russian troll factory

Researchers funded by the U.K. government have identified a Russian troll factory that's working to spread misinformation on social media and in comment sections of popular websites.

The "sick" organization is working from St. Petersburg, with paid employees and internal working teams, the government said in a press release. Instead of relying on bots, which are automated accounts that spam content, the operation is using the messaging app Telegram to recruit and coordinate supporters who then target social media profiles with pro-war and pro-Kremlin content.

The activities are being directed at senior international politicians and media outlets on platforms such as Twitter, Facebook and TikTok.

"We cannot allow the Kremlin and its shady troll farms to invade our online spaces with their lies about Putin's illegal war," Foreign Secretary Liz Truss said in a statement. "The UK Government has alerted international partners and will continue to work closely with allies and media platforms to undermine Russian information operations."

— Jessica Bursztynsky

About 100 evacuated so far from Mariupol's Azovstal, Zelenskyy says

A group of about 100 civilians have been evacuated from Mariupol's Azovstal steel plant and are heading to a controlled area, Ukrainian President Volodymyr Zelenskyy said in a tweet.

"Evacuation of civilians from Azovstal began," Zelenskyy said. "The 1st group of about 100 people is already heading to the controlled area. Tomorrow we'll meet them in Zaporizhzhia. Grateful to our team! Now they, together with #UN, are working on the evacuation of other civilians from the plant."

The Ministry of Foreign Affairs shared photos of evacuees, saying it welcomed the civilians to Ukrainian-controlled territory.

Russia's attempt to take over Mariupol has led to dire conditions in the port city. Thousands have been trying to survive without food, water, sanitation or medical care.

A few thousand civilians and Ukrainian fighters have been sheltering in Azovstal. Aid groups and the governments have been working to evacuate civilians, but efforts have been repeatedly stalled. Ukraine has previously accused Russia of blocking efforts to evacuate civilians from Mariupol.

The Mariupol City Council said in a Telegram post that humanitarian evacuations located in other parts of the city were postponed to Monday morning due to "security reasons."

— Jessica Bursztynsky

Polish authorities say nearly 1 million people crossed the border into Ukraine

Nearly 1 million people have crossed the border into Ukraine, the Polish Border Guard said.

Since Feb. 24, 975,000 people have crossed back into Ukraine from Poland, while roughly 3.08 million people made the reverse journey, authorities said on Twitter.

On Saturday, 26,800 people returned to Ukraine, while 23,500 fled Ukraine into Poland, they added.

Poland has taken in about 3 million of the more than 5 million Ukrainians who have fled the country since Russia attacked in late February. The influx put considerable strain on Ukraine's closest neighbor.

Warsaw's Mayor Rafal Trzaskowski has said the capital city is at "capacity." 

— Jessica Dickler

EU is reportedly working to send Ukraine additional emergency funding

The European Union is working on a new round of emergency funding for Ukraine, an official told the Financial Times.

In addition to a new round of lending, the bloc is working on accelerating the payment of 600 million euros under an existing emergency support plan, European Commission Executive Vice President Valdis Dombrovskis told the FT.

Brussels could either add to its funding or extend a new emergency loan, Dombrovskis told the outlet.

"We are currently assessing both options," Dombrovskis said in an interview with the Financial Times. "The aim is of course to really bridge this financing gap."

Ukraine has called for immediate financial support to fill a budget gap following Russia's full-scale invasion. President Volodymyr Zelenskyy said late last month that the Eastern European nation needs $7 billion per month to make up for economic losses caused by the war.

Read the full story from the Financial Times here.

— Jessica Bursztynsky

Fourteen more people evacuated from Azovstal plant, Reuters photographer says

A group of 14 more people arrived on Sunday at a temporary accommodation center after leaving the area around the Azovstal steel plant in Ukraine's Mariupol, a Reuters photographer said.

Reuters photographs showed earlier on Sunday around 40 civilians arriving at the center in the village of Bezimenne in the Donetsk Region.

— Reuters

Ukraine's foreign minister discussed further sanctions with Blinken

Foreign Minister Dmytro Kuleba said he was grateful to the U.S. for standing by Ukraine "resolutely" after speaking with U.S. Secretary of State Antony Blinken.

"We discussed further sanctions on Russia, arms deliveries and financial support to Ukraine," Kuleba said in a tweet.

It comes after a U.S. Congressional delegation, led by House Speaker Nancy Pelosi, visited Kyiv, Ukraine's capital, and met with President Volodymyr Zelenskyy.

— Katrina Bishop

Pope says Mariupol has been 'barbarously bombarded'

Pope Francis has said the embattled city of Mariupol had been "barbarously bombarded and destroyed" in his noon address Sunday.

Speaking to crowds gathered at St Peter's Square, the pope said the war in Ukraine makes him "suffer and cry."

"My thoughts go immediately to the Ukrainian city of Mariupol, the city of Mary, barbarously bombarded and destroyed," he said.

"Even now, even from here, I renew my call for the creation of safe humanitarian corridors for the people trapped in the steelworks of that city. I suffer and cry when I think of the suffering of the Ukrainian people, particularly the weakest, the elderly and children."

— Katrina Bishop

Evacuation from Mariupol planned for Sunday

Mariupol City Council says it should be possible for citizens to leave the besieged city of Mariupol on Sunday.

Writing on Telegram, the council said those wishing to leave should meet at 4 p.m. local time (9 a.m. ET). The plan is for them then to be taken to Zaporizhzhia, a city in southeastern Ukraine.

"Officially. Today it is possible to evacuate civilians from Mariupol to Zaporizhzhia. Gathering of people at 16:00 near the shopping center 'Port City,'" the post said.

"If you have relatives or acquaintances in Mariupol, try to contact them in all ways. Call, write and say that it is possible to go to Zaporizhzhia, where it is safe. We pray that everything works!"

Previous attempts to let civilians leave the city safely via humanitarian corridors have mostly failed. Ukrainian officials say satellite images captured by Maxar show mass graves 20 times bigger than a cemetery discovered in the city of Bucha this month.

— Katrina Bishop

Heavy shelling continues in Donetsk, Ukraine says

Russian forces are continuing their onslaught in eastern Ukraine, with 14 shelling attacks reported in the Donetsk region last night, according to Ukraine's Ministry of Interior Affairs.

"Last night, Russian troops shelled Donetsk region 14 times. The Russians killed civilians. There are also wounded, including children aged 5, 6, 7 and 14," the ministry said in an update on Telegram.

"At least 24 civil facilities were destroyed: residential buildings, a kindergarten, a community center, and a factory."

Ukraine said Russia used aircraft, multiple launch rocket systems, tanks and heavy artillery to fire at Mariupol, Lyman, Avdiivka, Dobropillya, Ocheretyn, Drobyshevo, Novosilka, Dibrovo and Pisky.

Donetsk, in eastern Ukraine, has been a longtime focus for Russia and is home to a separatist "republic," along with Luhansk. Both are in the Donbas region, a strategic target for Russia, with political, ideological and economic importance.

— Katrina Bishop

U.S. lawmakers visit Kyiv with the message: 'America stands firmly with Ukraine'

A U.S. Congressional delegation visited Ukraine Sunday — the first to do so since Russia's invasion of the country in February.

"Our delegation traveled to Kyiv to send an unmistakable and resounding message to the entire world: America stands firmly with Ukraine," the group said in a statement.

The lawmakers met with Ukrainian President Volodymyr Zelenskyy in Kyiv, who posted a visit of their meeting on Telegram.

"He conveyed the clear need for continued security, economic and humanitarian assistance from the United States to address the devastating human toll taken on the Ukrainian people by Putin's diabolic invasion – and our delegation proudly delivered the message that additional American support is on the way, as we work to transform President Biden's strong funding request into a legislative package," the statement went on to say.

The delegation consisted of Speaker Nancy Pelosi, Chairman Jim McGovern, Chairman Gregory Meeks, Chairman Adam Schiff, Congresswoman Barbara Lee, Congressman Bill Keating and Congressman Jason Crow. All members, bar Lee and Keating, entered Ukraine.

They are now in Poland and due to visit the country's capital, Warsaw.

— Katrina Bishop

Russia wants to impose 'strong political and economic influence' over Kherson, UK says

Russia is introducing its currency into the Ukrainian city of Kherson from today, according to the U.K.'s Ministry of Defence.

In its latest intelligence update on Twitter, the ministry said Russia has been seeking to legitimize its control of the city since seizing it in March and is looking to exert "strong political and economic influence" in the area.

"Recent statements from this administration include declaring a return to Ukrainian control 'impossible' and announcing a four-month currency transition from the Ukrainian hryvnia to the Russian rouble. The Russian rouble is due to be used in Kherson from today," the tweet said.

Kherson is a strategically important port city for Russia, just over 100 kilometers from Crimea, which the Kremlin annexed from Ukraine in 2014.

"Enduring control over Kherson and its transport links will increase Russia's ability to sustain its advance to the north and west and improve the security of Russia's control over Crimea," the U.K. added.

Also on Sunday, Russia's state-controlled media claimed that Ukraine "nationalists" had shelled the villages of Kiselevka and Shiroka Balka in the Kherson region. Those claims cannot be independently verified by NBC.

Separately, the Kyiv Independent reported this weekend that mobile and internet services had been shut down in the Kherson oblast (or administrative district).

— Katrina Bishop

Nancy Pelosi visits Kyiv

President Volodymyr Zelenskyy says he met with Speaker of the House Nancy Pelosi in Ukraine's capital.

Posting a Telegram video that shows the pair meeting and shaking hands, Zelenskyy described the United States as a "leader in strong support" for Ukraine.

"Meeting with the Speaker of the U.S. House of Representatives Nancy Pelosi in Kyiv. The United States is a leader in strong support of Ukraine in the fight against Russian aggression. Thank you for helping to protect the sovereignty and territorial integrity of our state!" he wrote, according to an NBC translation.

— Katrina Bishop

'Every Russian soldier can still save his own life': Zelenskyy urges invading troops not to fight

Ukrainian President Volodymyr Zelenskyy switched into Russian in his nightly video address to urge Russian soldiers not to fight in Ukraine, saying even their generals expected that thousands of them would die.

He said Russia has been recruiting new troops "with little motivation and little combat experience" for the units that were gutted during the early weeks of the war so these units can be thrown back into battle.

He said Russian commanders fully understand that thousands of them will die and thousands more will be wounded in the coming weeks.

"The Russian commanders are lying to their soldiers when they tell them they can expect to be held seriously responsible for refusing to fight and then also don't tell them, for example, that the Russian army is preparing additional refrigerator trucks for storing the bodies. They don't tell them about the new losses the generals expect," Zelenskyy said late Saturday.

"Every Russian soldier can still save his own life. It's better for you to survive in Russia than to perish on our land," he said.

— Associated Press

Poland struggles to house 2.9 million refugees; Warsaw rental prices soar

More than 5 million Ukrainians have fled their country since Russia attacked in late February, and the country that has taken in more than half of them is showing signs of strain.

NBC News reported over the weekend that Poland has given shelter to about 2.9 million Ukrainians, but the NATO country is running low on everything from classrooms to housing.

The population of Warsaw, Poland's capital, has grown by 15 percent since the war started.

Mayor Rafal Trzaskowski visited the United States this week to ask for more help from the international community, NBC News said. He warned that Warsaw is unable to absorb another wave of refugees.

Thousands of Poles have welcomed Ukrainians into their homes, but many have already filled their spare rooms.

The number of Warsaw apartments available for rent has fallen, NBC News said, with rental prices rising more than 30 percent since the end of February.

Read the full NBC News report here.

— Ted Kemp

Sweden says Russian plane violated its airspace

Sweden says a Russian military plane has violated Swedish airspace.

The incident happened late Friday in the Baltic Sea near the island of Bornholm.

In a statement Saturday, the Swedish Armed Forces said a Russian AN-30 propeller plane flew toward Swedish airspace and briefly entered it before leaving the area.

The Swedish Air Force scrambled fighter jets that photographed the Russian plane.

Swedish Defense Minister Peter Hultqvist told Swedish public radio that the violation was "unacceptable" and "unprofessional."

In a similar incident in early March four Russian warplanes violated Swedish airspace over the Baltic Sea.

Sweden and neighboring Finland are both considering NATO membership following Russia's invasion of Ukraine. Moscow has warned that such a move would have consequences, without giving specifics.

— Associated Press

Ukraine says 20 civilians evacuated from besieged Azovstal steel plant in Mariupol

A Ukrainian commander said 20 civilians were evacuated Saturday from the Azovstal steel plant in the besieged city of Mariupol, according to a video posted to Telegram and translated by NBC News.

Earlier in the day, Russian state media had reported that 25 civilians were evacuated from the plant. CNBC could not independently confirm either claim.

In recent weeks, Russian forces had all but surrounded the strategic coastal town of Mariupol making the steel facility the city's last stronghold.

United Nations Secretary-General Antonio Guterres said he personally requested that Russian President Vladimir Putin and Russian Foreign Minister Sergey Lavrov coordinate an evacuation for civilians trapped in the steel facility during in-person talks in Moscow last week. Following discussions in Moscow, Guterres traveled to Kyiv to meet with Ukrainian President Volodymyr Zelenskyy.

— Amanda Macias

Read CNBC's previous live coverage here:

Zelenskyy speaks directly to Russian troops in nightly address; Russians violate Swedish airspace