An attack on Russia's Black Sea Fleet in the city of Sevastopol earlier this week has "functionally destroyed" a ship and caused "catastrophic damage" to a submarine, the UK Ministry of Defence said.

In its daily update on the war, the ministry said multiple missiles struck the landing ship Minsk and Kilo 636.3 class submarine Rostov-na-Donu, while they were undergoing maintenance.

"Despite the Russian Ministry of Defence downplaying the damage to the vessels, open-source evidence indicates the Minsk has almost certainly been functionally destroyed, while the Rostov has likely suffered catastrophic damage," the ministry said on social media.

It added that efforts to restore the submarine to service are likely to "take many years and cost hundreds of millions of dollars." 

The ministry also highlighted the possibility that the dry docks will remain out of use for many months due to the "complex task" of removing the wreckage from them.

"This would present the BSF [Russia's Black Sea Fleet] with a significant challenge in sustaining fleet maintenance," it said. 

It added that Rostov was among the fleet's four cruise-missile capable submarines and had played a major role in striking Ukraine, highlighting the impact of its loss on Russia's power across the Black Sea and Eastern Mediterranean.

On Wednesday, Russia's Defense Ministry said that a Ukrainian cruise missile attack on a shipyard in the city of Sevastopol damaged two ships undergoing repairs.