(Reuters) - Russia's Black Sea fleet retains the ability to strike Ukrainian and coastal targets, despite its losses of the landing ship Saratov and the cruiser Moskva, Britain's defence ministry said on Thursday.

       About 20 Russian Navy vessels, including submarines, are in the Black Sea operational zone, the ministry said on Twitter.

       "The Bosphorus Strait remains closed to all non-Turkish warships, rendering Russia unable to replace its lost cruiser Moskva in the Black Sea," it added in the regular bulletin.

       Reuters could not immediately verify the report.

       (Reporting by Rachna Dhanrajani in Bengaluru; Editing by Clarence Fernandez)