Russia has reported the flagship of the country's Black Sea fleet has sunk.
The Russian Defence Ministry claimed the Moskva missile-guided cruiser sank in a storm on Thursday after being gutted by fire, they say the fire caused ammunition to detonate and blow up.
Maksym Marchenko, the Ukrainian governor of the region around the Black Sea port of Odesa, said Ukrainian forces struck the cruiser with two missiles and caused "serious damage".
Ukrainian officials had already claimed the ship was sunk, describing it as a “resounding slap in the face” to Moscow’s forces.
Neither sets of claims has been independently verified.
Russia's defence ministry previously said the entire crew of the Moskva, which usually has about 500 people on board, was evacuated.
How much of a blow was the sinking of the Moskva to the Kremlin? Rohit Kachroo explains
As Global Security Editor Rohit Kachroo notes, the Pentagon has said that four or five other Russian warships have now backed away from the Ukraine coastline- possibly as a consequence of the sinking of the cruiser.
The Moskva is the same ship Ukrainians defending Snake Island, off the south coast, told to go "f*** yourself" after Russians demanded they surrender.
Officials said the soldiers - who made headlines around the world - had been killed moments after their defiant message.
But the group was actually taken prisoner, said Ukrainian officials, who were later released from captivity as part of a prisoner exchange with Russian forces.
Satellite images showed the Moskva cruiser in and close to the Black Sea port of Sevastopol, in Crimea, days before it was damaged, on April 7 and April 10, according to Maxar Technologies.
The Moskva cruiser is the second major Russian ship known to have suffered serious damage since Moscow invaded Ukraine, after tank carrier Orsk was hit and set on fire in the Sea of Azov in late March.
Ukraine claimed on Thursday it had destroyed the Russian ship, capable of carrying 20 tanks, 45 armoured vehicles and 400 troops in the occupied port city of Berdyansk, and was a "huge target".
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The UK's Ministry of Defence (MoD) warned Russian President Vladimir Putin's speech on Tuesday - during which he repeated his statement that he had launched a "special military operation" against Ukraine to protect Russia - highlighted his focus remains firmly on eastern Ukraine.
It said Russia is striking Ukrainian forces in the Donbas region to prepare for a fresh attack, and that the towns of Kramatorsk and Kostiantynivka are likely to be targets for similar levels of violence seen in other urban centres throughout the invasion.
The MoD said: "The combination of widespread missile and artillery strikes and efforts to concentrate forces for an offensive represents a reversion to traditional Russian military doctrine.
"However, this will require significant force levels. Ukraine’s continued defence of Mariupol is currently tying down significant numbers of Russian troops and equipment."
Meanwhile, Ukraine's army said on Thursday there is still "a constant threat" of Russia using missile weapons across Ukraine.
Armed Forces spokesperson Oleksandr Shputun said in a daily briefing that Russia continues carrying out "systematic strikes against military and civilian infrastructure" in Kharkiv, in the north-east, Zaporizhzhia, in the south-east, and the eastern region of Donetsk.
"The enemy continues to build up an aviation group near the eastern border of our state, reinforces artillery units and optimises the existing control, intelligence and medical support systems. There is a constant threat of the use of missile weapons by the enemy throughout the territory of Ukraine," he said.
Mr Shputun also said Russia is trying to conduct forced mobilisation in the "temporarily occupied territories" of the eastern Donetsk and Luhansk regions.
"In the city of Gorlovka, daily rounds in houses and multi-storey apartment buildings are carried out," he added.
He said that heavy fighting continues in the battered Donetsk Oblast city of Mariupol, where its mayor said more than 20,000 civilians have been killed and at least one war crime has been confirmed by European experts.
The reported ship attack by a Neptune cruise missiles comes in the same week President Joe Biden called Russia’s actions in Ukraine “a genocide” and approved $800 million (£609 million) in new military assistance to Kyiv, saying weapons from the West have sustained Ukraine’s fight so far and “we cannot rest now.”
The munitions include artillery systems, armoured personnel carriers and helicopters.
Ukrainian President Volodymyr Zelenskyy said he’s “sincerely thankful” to the US for the new round of military assistance, and that he and President Biden had discussed on the phone even tougher sanctions against Moscow, as well as efforts to bring to justice Russian soldiers who committed war crimes in Ukraine.
In his daily late-night address to the nation, Mr Zelenskyy also said he was thankful for Wednesday’s visit by the presidents of Poland, Estonia, Lithuania and Latvia.
He said those leaders “have helped us from the first day, those who did not hesitate to give us weapons, those who did not doubt whether to impose sanctions.”
Mr Zelenskyy also said work was continuing to clear tens of thousands of unexploded shells, mines and tripwires that were left behind in northern Ukraine by the retreating Russians.
In the latest in a string of senior European politicians to make the trip to show support for Ukraine, Ireland’s foreign minister travelled to Kyiv on Thursday and planned to discuss how Ireland can “assist Ukraine in its application for EU candidate status.”