The Russian Defense Ministry said that the main ship of the Russian Black Sea Fleet - the missile cruiser Moskva - was badly damaged after an explosion of ammunition on board, while Ukraine said it hit the ship itself with a missile strike.
"As a result of a fire in the missile cruiser Moskva, an ammunition exploded. The ship was seriously damaged," the ministry said in a statement.
The Interfax news agency quoted the ministry as confirming that all crew members of the ship had been evacuated, and indicated that the cause of the fire was being investigated.
The blast represented another military setback for Russia, which has suffered a series of blows since it invaded Ukraine on February 24, which Moscow describes as a "special military operation" aimed at "de-Nazification" of its neighbour.
Russian news agencies said Moskva, which began operating in 1983;
It was armed with 16 Vulcan anti-ship cruise missiles with a range of at least 700 km.
In April 2021, the agency quoted a retired Russian admiral as saying that "this is the most dangerous ship in the Black Sea."
Ukrainian novel
Earlier on Wednesday, the governor of Ukraine's Odessa region announced that his country's forces had hit a Russian warship in the Black Sea with a missile strike.
"The Neptune missiles protecting the Black Sea caused very severe damage to the Russian ship. Glory to Ukraine," Governor Maxim Marchenko said on Telegram.
For his part, Ukrainian presidential advisor Oleksiy Aristovich said that "a surprise hit the main ship of the Russian Black Sea Fleet Moskva."
"It's burning really hard. Now. In these stormy conditions we don't know if she can receive help. There are 150 people on board," he said in a YouTube recording. "We don't understand what happened."