A Russian frigate tracked a US submarine in the Mediterranean Sea in April, the Kremlin said.
The frigate Admiral Essen tracked the Ohio-class submarine for more than to hours while it was in the area during a period of heightened tension as Britain, France and the US were bombing Syria after the regime of President Bashar Al-Assad struck the town of Douma with chemical weapons.
The US Department of Defence has not commented on the claims. The Ohio-class ballistic-missile submarines are some of the quietest, stealthiest submarines in the world.
The Russian ship left Sevastopol, a major Black Sea port located on the Crimean Peninsula, on 13 March and returned on 30 June.