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

Russian forces are consolidating their hold on Avdiivka after capturing the city at the weekend. Russian troops say they have now taken full control of the Donetsk city's chemical and coke plant.

Russian news agency Tass, citing Russia's Defense Ministry, stated that Russian forces had now "completely liberated the coke plant in Avdiivka, the flags of the Russian Federation have been hoisted on the buildings of the enterprise."

Russia's Defense Ministry said Sunday that some Ukrainian units were still entrenched at the plant, which used to be one of the largest of its kind in Europe.

Ukrainian authorities said on Sunday that they've launched an investigation into the alleged shooting of unarmed Ukrainian prisoners of war in Avdiivka and the village of Vesele.

In other news, the widow of Russian opposition leader Alexei Navalny said on Monday that she would continue her husband's fight for a free Russia. Yulia Navalnaya called on supporters to maintain their opposition to Russian President Vladimir Putin.

Republican front-runner Donald Trump addressed Navalny's death with a post on Truth Social on Monday, breaking his silence after coming under fire for not commenting on the matter over the weekend. The post did not mention Putin or Russia, however.

Biden administration is leaning toward supplying Ukraine with long-range missiles

After months of requests from Ukrainian officials, the Biden administration is working toward providing Ukraine with powerful new long-range ballistic missiles, according to two U.S. officials.

Late last year, the U.S. began to supply Ukraine with Army Tactical Missile Systems, known as ATACMS, but so far it has provided only the older medium-range ATACMS. Now, the U.S. is leaning toward sending the longer-range version of the missile, the officials said, which would allow Ukraine to strike farther inside the Russian-held Crimean Peninsula. 

But U.S. funding for arms shipments to Ukraine remains uncertain because of opposition from former President Donald Trump and his Republican allies in Congress. Last week the Senate passed a $95 billion foreign aid package for Ukraine, Israel and Taiwan. But it's not clear whether or when the GOP-controlled House will vote on the measure or whether it would survive the vote.

Read the full story here.

— NBC News

Trump breaks silence on Navalny — without mentioning Russia or Vladimir Putin

Republican front-runner Donald Trump on Monday addressed the death of Russian opposition leader Alexei Navalny, who died in a Russian prison colony on Friday.

"The sudden death of Alexei Navalny has made me more and more aware of what is happening in our Country. It is a slow, steady progression, with CROOKED, Radical Left Politicians, Prosecutors, and Judges leading us down a path to destruction," Trump wrote in a post on social media platform Truth Social.

"Open Borders, Rigged Elections, and Grossly Unfair Courtroom Decisions are DESTROYING AMERICA. WE ARE A NATION IN DECLINE, A FAILING NATION," he added.

Trump had been silent on Navalny's death until Monday, whilst various other U.S. politicians including President Joe Biden and Trump's fellow Republican presidential candidate Nikki Haley have said Russian President Vladimir Putin is responsible.

The Kremlin has rejected these allegations, with the Russian foreign ministry calling the reaction from political leaders "self-exposing," given that no forensic medical examination has yet been made available.

Haley also reacted to Trump's post on Monday about Navalny. In a post on social media platform X she said that he could have condemned Putin or praised Navalny, but instead denounced America and compared it to Russia.

— Sophie Kiderlin

U.S. considering sanctioning Chinese firms aiding Russia’s war

The U.S. is considering slapping sanctions on Chinese companies it believes are helping Russia fuel its war in Ukraine, members of Congress told CNBC, marking the first direct apportioning of blame toward Beijing since the start of the war.

Democratic Senator Gerald Connolly, member of the U.S. House Committee on Foreign Relations, on Saturday said that lawmakers were already considering such plans after similar measures were proposed last week by the European Union.

Read the full story here.

— Karen Gilchrist

Russia says Ukraine poisoned governors of two annexed Ukrainian provinces

Russia's Defence Ministry said on Monday that Ukraine poisoned the Moscow-installed governors of Ukraine's Kherson and Luhansk regions, though both were still alive.

In a briefing published online, the ministry said Ukraine poisoned Moscow-appointed Luhansk governor Leonid Pasechnik in December 2023, and Kherson head Vladimir Saldo in August 2022.

Kherson and Luhansk regions were among four Ukrainian provinces that Russia declared it had annexed in September 2022, even though it did not fully control any of them.

The briefing said that on Dec. 5 Pasechnik, a former officer in Ukraine's SBU security service turned pro-Russia separatist, "received severe poisoning with phenolic compounds". It gave no information about the current state of his health.

It said that Saldo, a former mayor of Kherson city and pro-Russian lawmaker in Ukraine's parliament, had been hospitalised on Aug. 9, 2022, with symptoms of poisoning.

Russian-installed authorities in Kherson said in August 2022 that Saldo had fallen sick, but did not say that he had been poisoned. Saldo has since returned to public prominence in the Russian-controlled part of Kherson region.

Ukraine has staged a string of attacks against Russian-installed officials in Moscow-held parts of the country since tens of thousands of Russian troops entered the country in February 2022.

Several targets have been killed and more wounded in bombings and shootings that Moscow has blamed on Ukraine.

Zelenskyy visits front line after Avdiivka blow

Ukraine's President Volodymyr Zelenskyy has visited troops on the northeastern front line, trying to boost morale after a significant withdrawal from Avdiivka in Donetsk, eastern Ukraine.

Posting on Telegram, Zelenskyy said he had visited a command post of the brigade that is defending the Kupiansk region of Kharkiv in northeastern Ukraine.

Zelenskky said he had discussed "important issues with the brigadier general, talked with the soldiers, and presented them with awards."

The visit Monday comes after Ukraine's military leadership decided to withdraw troops from the industrial city of Avdiivka in Donetsk after months of intense battles to defend the town.

— Holly Ellyatt

Russia says an investigation into Navalny's death is underway

Kremlin spokesperson Dmitry Peskov on Monday confirmed an investigation is underway into the death of Russian opposition leader Alexei Navalny and insisted that "all due actions are being taken" to determine the circumstances surrounding his demise.

Earlier on Monday, Navalny's spokesperson Kira Yarmysh said that Navalny's mother and lawyers had been blocked from entering a mortuary where his body could be being kept.

CNBC could not independently verify the report. The Kremlin has denied any involvement in blocking the return of Navalny's body to his relatives.

Here's the full story.

— Sam Meredith

Navalny's widow Yulia: I will continue my husband's fight for a free Russia

Yulia Navalnaya, the widow of Russian opposition leader Alexei Navalny, said on Monday that she would continue her husband's fight for a free Russia and called on supporters to battle President Vladimir Putin with greater fury than ever.

"I want to live in a free Russia, I want to build a free Russia," Navalnaya said in a video message entitled "I will continue the work of Alexei Navalny".

"Vladimir Putin killed my husband," Navalnaya said, adding that she would work with the Russian people to battle with the Kremlin to create a new Russia.

The Kremlin has denied involvement in his death.

"By killing Alexei, Putin killed half of me - half of my heart and half of my soul," Navalnaya said.

"But I still have the other half, and it tells me that I have no right to give up. I will continue the work of Alexei Navalny, continue to fight for our country."

"I urge you to stand next to me," she said. "I ask you to share the rage with me. Rage, anger, hatred towards those who dared to kill our future."

Navalnaya accused the Russian authorities of hiding Navalny's body and of waiting for traces of the Novichok nerve agent to disappear from his body.

"We know exactly why Putin killed Alexei three days ago," she said. "We will tell you about it soon. We will definitely find out who exactly carried out this crime and how exactly. We will name the names and show the faces."

Kremlin slams West's 'unacceptable' reaction to Navalny's death

The Kremlin slammed the West's reaction to Alexei Navalny's death, saying statements from Western politicians condemning Navalny's death in Russian custody were "unacceptable."

Russian Presidential Press Secretary Dmitry Peskov said the results of an investigation into Navalny's sudden death on Friday had not yet been made public.

"In this regard, they [the results] are not known. Therefore, in conditions when there is no real information, we consider it absolutely unacceptable to make such, let's say, frankly boorish statements," Peskov told reporters RIA Novosti reported.

"This is not befitting government officials, from whom we heard such statements," Peskov told reporters, commenting on the reaction of Western politicians to Navalny's death.

Western officials have been highly critical of the Kremlin following Navalny's death in a Russian penal colony, saying there was little doubt in their eyes that Russian President Vladimir Putin was ultimately responsible for the death of his political opponent. Putin has not directly responded to the criticism.

Navalny's spokesperson Kira Yarmysh said Monday that his mother and lawyers had been told that the official verification of the cause of death had been extended and that it was unclear how long it would take.

"The cause of death is 'undetermined'," Yarmysh said, adding that the Russian authorities were lying and stalling, Reuters reported.

— Holly Ellyatt

Public figures under pressure to support war in Russia

Public figures in Russia continue to face "substantial" pressure to display overt support for the war in Ukraine, Britain's Ministry of Defense noted Monday.

Pressure has risen on particular celebrities following a high-profile scandal over a "nearly naked" party in Moscow in December.

"The aftermath of the 'nearly naked' party scandal demonstrates the increasingly pervasive presence of the war in public life," the U.K.'s Defense Ministry said in an intelligence update Monday.

"The Kremlin almost certainly intentionally amplified and exploited the scandal, seeking to portray a contrast between Russians 'patriotically' supporting the war effort and a hedonistic 'Westernised' metropolitan elite," it noted on X.

One attendee of the party was jailed, fined under so-called "LGBT propaganda" laws, and served with a summons to a military conscription office, the ministry noted.

Many celebrities who attended the Moscow party have since issued apologies, some begging for forgiveness as their careers have suffered following the moral outrage over the party.

This week, it was reported that Russian pop star Filipp Kirkorov — reportedly "blacklisted" by the Kremlin for attending the party — performed and visited wounded soldiers in occupied Ukraine.

Independent Russian online news outlet Meduza reported that a "blacklist" of 50 artists had been circulated by the Kremlin to Russian concert promoters, effectively banning them from performing in Russia. The list reportedly included public opponents of the war alongside others — such as Kirkorov — who had provoked the ire of the Kremlin for other reasons.

— Holly Ellyatt

Russia says 'large number' of Ukrainians captured in Avdiivka

A large number of Ukrainian prisoners have been captured in Avdiivka, according to a Russian official in the region.

Denis Pushilin, the head of the separatist, pro-Russian "Donetsk People's Republic" in eastern Ukraine, told the Rossiya-24 TV channel that a significant number of Ukrainian soldiers had surrendered when Russian forces captured Avdiivka at the weekend.

“There are quite a large number of prisoners ... In general terms, I can say that the enemy was forced to surrender in order to save his life. And the information that I have is quite a considerable amount,” Pushilin said, news agency Tass reported.

Ukraine has not commented on the number of soldiers that were captured as its forces withdrew from Avdiivka, a move it ordered late last week, it said, to avoid being surrounded. Ukrainian authorities said on Sunday that they've launched an investigation into the alleged shooting of unarmed Ukrainian prisoners of war in Avdiivka and the village of Vesele, however. Russia has not commented on the allegations.

The seizing of Avdiivka is a significant milestone for Russian forces after months of intense fighting over the industrial city. Russia sees the victory as a step toward occupying the whole of the Donetsk region and wider Donbas area of eastern Ukraine.

Russia's Defense Ministry said its forces are now continuing "offensive actions to further liberate the Donetsk People's Republic," a region Moscow declared a part of the Russian Federation in late 2022.

— Holly Ellyatt

Russia has yet to establish official cause of Navalny death, spokeswoman says

Russian investigators have not yet established the cause of Alexei Navalny's death and it is unclear how long it will take for official conclusions to be made, his mother was told, Navalny's spokeswoman said on Monday.

Navalny, a 47-year-old former lawyer, fell unconscious and died on Friday after a walk at the "Polar Wolf" penal colony in Kharp, about 1,900 km (1,200 miles) northeast of Moscow, where he was serving a three-decade sentence, the prison service said.

Navalny's mother, Lyudmila, was told on Saturday at the prison colony that he had perished from "sudden death syndrome", a vague term for different heart conditions that end in death, according to Navalny's team.

Navalny's spokeswoman, Kira Yarmysh, said that his 69-year-old mother, and lawyers were told that the official verification of the cause of death had been extended and that it was unclear how long it would take.

"The cause of death is 'undetermined'," Yarmysh said, adding that the Russian authorities were lying and stalling.

His mother and lawyers were not allowed into the morgue on Monday in the Arctic town near the prison colony where the authorities said he dropped dead, Yarmysh said.

"Asked if Alexei's body was there, the staff did not answer," said Yarmysh.

The death of Navalny, a former lawyer, robs the disparate Russian opposition of its most charismatic and courageous leader as President Vladimir Putin prepares for an election that will keep him in power until at least 2030.

— Reuters

Russian forces have reportedly taken control of Avdiivka's coke plant

Russian armed forces have reportedly taken full control of the chemical and coke plant in Avdiivka, the Donetsk city that was captured at the weekend after Ukraine withdrew its troops, fearing encirclement.

Russian news agency Tass, citing Russia's Defense Ministry, stated that Russian forces had now "completely liberated the coke plant in Avdiivka, the flags of the Russian Federation have been hoisted on the buildings of the enterprise."

Russia's Defense Ministry said on Sunday that some Ukrainian units were entrenched at the plant, one of the largest of its kind in Europe, which is located on northwestern outskirts of the city.

Russia's capture of Avdiivka represents its most significant victory in Ukraine since claiming control of Bakhmut in Donetsk last May. Tass reported Monday that military personnel had already begun to clear mines from roads and buildings in Avdiivka.

Ukraine's military leadership said the decision to withdraw soldiers from Avdiivka was made in order to save them from being surrounded.

"In a situation where the enemy is advancing on the corpses of their own soldiers with a ten-to-one shell advantage, under constant bombardment, this is the only correct solution," Oleksandr Tarnavskyy, Ukraine's army's commander in the Donetsk area, said on Telegram.

 "We did no allow to encircle us, the personnel has been withdrawn, our soldiers have taken up defense in the designated areas."

— Holly Ellyatt

Ukraine launches investigation into alleged shootings of unarmed POWs in Avdiivka

Ukrainian authorities say they have launched an investigation into the alleged shooting of unarmed prisoners of war in the recently Russian-captured towns of Avdiivka and Vesele in Donetsk, eastern Ukraine.

The Prosecutor Office of the Donetsk region said on Telegram Sunday that a "pre-trial investigation was launched into the facts of violation of the laws and customs of war, combined with intentional murder."

The prosecutor said that an unnamed Telegram channel had "published a message about the execution of 6 prisoners of the Armed Forces of Ukraine at one of the positions in the city of Avdiivka. The defenders were seriously injured and were waiting for evacuation."

"A video recording with a fragment of the murder of 2 more soldiers near the village was also discovered [in] Vesele," the regional prosecutor's office claimed.

"The recording from the drone camera shows how today, during the assault on our positions, a representative of the Russian Armed Forces shoots at close range, first at one captured soldier of the Armed Forces of Ukraine, and then at the second. Not wanting to leave the prisoners alive, the occupier deliberately kills them with automatic weapons," the post stated.

CNBC was unable to confirm the information within the report and Russia has not responded to Reuters' request for comment on the allegations, which come as Russian forces claimed to have taken full control of Avdiivka, and the village of Vesele, after months of brutal fighting in the area.

Capturing Avdiivka is Russia's biggest gain since it fully occupied the Donetsk city of Bakhmut in May last year.

— Holly Ellyatt

European leaders appeal for greater support for Ukraine

The West is suffering a "colossal failure of imagination" in thinking Russia's war in Ukraine will not hit them next, European policymakers have been told amid calls for a doubling down of transatlantic support for Kyiv.

Danish Prime Minister Mette Frederiksen criticized a waning sense of urgency among delegates at the Munich Security Conference on Saturday as Moscow's full-scale offensive nearly enters its third year.

"The sense of urgency is simply not clear enough in our discussions," Frederiksen told a lunchtime session. "We have to speed up and we have to scale up."

Denmark has now donated its entire artillery to Ukraine, Frederiksen said, urging other countries to do the same as the war marks its second anniversary on Feb. 24.

"On Saturday, there should be new deliveries," she said. "Words will not solve this situation."

Frederiksen's sentiment was echoed by others in the room. The policymakers were speaking at the 7th Munich Ukrainian Lunch, hosted on the sidelines of the MSC by the Yalta European Strategy (YES) forum and Ukrainian non-profit the Victor Pinchuk Foundation. Sweden's Foreign Minister Tobias Billström said countries must give Ukraine "what we already have."

The comments came hours after Ukrainian troops withdrew from the eastern city of Avdiivka, a longtime military stronghold, to avoid Russian encirclement. The fall of Avdiivka marks the biggest change on the frontlines since Moscow captured Bakhmut last May.

Read more here: 'It is urgent': European leaders appeal for greater support for Ukraine as Russia makes major gain