"Ukraine's armed forces made an unsuccessful attempt to attack the Black Sea Fleet's Priazovye ship," the Russian defence ministry said, adding Kyiv's forces used six unmanned boats.

"All the boats have been destroyed," the ministry said in a statement. "There are no casualties.".

The Priazovye battleship, which has been guarding the TurkStream and the Blue Stream gas pipelines, continues to perform its tasks, the defence ministry said.

A remotely piloted US military aircraft called the RQ-4 Global Hawk was conducting reconnaissance in the Black Sea at the time of the attack, Moscow said.