A Russian warship that was damaged by an explosion on Wednesday has sunk, Russia's defence ministry has said.
Moskva, the flagship of Russia's Black Sea Fleet, was being towed to port when "stormy seas" caused it to sink, according to a ministry message.
The 510-crew missile cruiser was a symbol of Russia's military power, leading its naval assault on Ukraine.
Kyiv says its missiles hit the warship. Moscow has not reported any attack - it says the vessel sank after a fire.
The blaze caused the explosion of the warship's ammunition, Russia says, adding that the entire crew were later evacuated to nearby Russian vessels in the Black Sea.
After saying initially the warship was afloat, late on Thursday the Russian defence ministry announced that the Moskva had been lost.
"While being towed... towards the destined port, the vessel lost its balance due to damage sustained in the hull as fire broke out after ammunition exploded. Given the choppy seas, the vessel sank," the Russian defence ministry said.
Ukrainian military officials said they struck the Moskva with Ukrainian-made Neptune missiles - a weapon designed after Russia's annexation of Crimea in 2014, and the naval threat to Ukraine in the Black Sea grew.
The ship's sinking was described by the US as a "big blow", but American officials were unable to confirm whether Ukrainian Neptune missiles were responsible.
"It's certainly plausible and possible that [Ukraine] did in fact hit this with a Neptune missile or maybe more," Pentagon spokesman John Kirby said to CNN.
A senior Ukrainian official said as many as 510 crew could have been on board the Moskva.
Originally built in the Soviet-era, the Moskva entered service in the early 1980s. The vessel was actually laid down in Ukraine's southern city of Mykolaiv, which has been heavily bombed by Russia in recent days.