"The forces of the Black Sea Fleet have begun to monitor the activities of the UK Navy's Dragon destroyer vessel, which entered the Black Sea on October 4," a statement read.
Use of the Black Sea by non-Black Sea-adjacent states is limited by the Montreux Convention of 1936, which allows warships from outside powers to remain in the body of water for no more than 21 days.
Additionally, no more than nine foreign warships, with a total tonnage of 15,000 tonnes, are allowed to be present in the Black Sea at any one time.