The former commander of Russia's Northern Fleet Alexander Moiseyev has been appointed acting commander-in-chief, replacing outgoing Admiral Nikolai Yevmenov, who had been in post since May 2019, the RIA news agency reported.

"Moiseyev was introduced as the Russian Navy's acting commander-in-chief at a ceremony," the agency said.

The Kremlin last week refused to comment on Moiseyev's appointment, which marks the biggest shakeup in Russia's military top brass in months.

Ukrainian forces claim to have destroyed more than two dozen Russian ships since the conflict began in February 2022, including a military patrol boat earlier this month.

The sinkings have been an embarrassment for Moscow, which has been forced to move boats from its historic Sevastopol naval base in Crimea to the port of Novorossiysk, further east.

Russia's Black Sea woes come in stark contrast to its land offensive in east Ukraine, where its forces have advanced in recent months after over a year of deadlocked fighting.