Russian and Chinese warships carried out their first joint patrols in the Pacific Ocean, Moscow said.
The two countries, which held naval maneuvers together in the Sea of Japan earlier this month, have forged closer military and diplomatic ties in recent years as relations with the West have deteriorated.
Combined Russia and China fleet included destroyers, frigates, a supply ship and a missile pursuit ship.
The naval exercise was closely watched by Japan, who said earlier this week that a group of 10 Chinese and Russian ships had crossed the Tsugaru Strait, separating the main island of Japan and its northern island of Hokkaido in the western Pacific.
The middle of the 100-mile stretch of sea, which is 15 to 25 miles (24 to 40 km) wide, is considered international waters.
Japanese territorial waters in the region are only three miles offshore, instead of the normal 12 miles.
This dates back to a Cold War deal, to allow US warships and nuclear-weapon submarines to transit through the strait without violating Japan’s arms ban on its territory.
The Russian Defense Ministry said in the statement: “The group of ships crossed the Tsugaru Strait for the first time as part of the patrol.
“The tasks of the patrols were the demonstration of the flags of the Russian and Chinese states, the maintenance of peace and stability in the Asia-Pacific region and the supervision of the subjects of the maritime economic activities of the two countries.”