The Russian Defense Ministry announced on Thursday that its Black Sea Fleet flagship vessel, Moskva, sunk after losing its stability when it was towed to a port. Russia said the ship sustained damages during a fire started by the detonation of ammunition. 

Ukrainian government officials, on Wednesday, claimed its armed forces fired missiles that struck the vessel, causing damage.

Ukrainian presidential adviser Oleksiy Arestovych and Anton Gerashchenko, an adviser to Ukraine's Ministry of Internal Affairs, said there was an explosion and that the cruiser is on fire.

The governor of Odessa Maksym Marchenko claimed on Telegram that two anti-ship cruise missiles struck the cruiser in the Black Sea, causing "very serious damage."

Russia earlier said the ship was seriously damaged, but did not confirm that was due to Ukrainian strikes. Russia claimed a fire abroad the ship forced all 510 members of the crew to evacuate.

"As a result of a fire, ammunition has detonated on the Moskva missile cruiser. The ship was seriously damaged. The crew was completely evacuated," the Russian Defense Ministry said in a statement.

"The cause of the fire is under investigation," the statement said.

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Russia later said the fire aboard the ship was contained and that the Moskva will be towed to a port. Russia's Defense Ministry said the main missile weapons on board were not damaged, but made no mention of missile strikes in its statement.