A group of 10 military vessels from China and Russia sailed through a narrow strait separating Japan's main island and its northern island of Hokkaido on Monday, the Japanese defense ministry said on Tuesday.
It was the first time Japan, which closely monitors military exercises in its region, has confirmed the passage of Chinese and Russian naval vessels sailing together through the Tsugaru Strait, which separates the Sea of Japan from the Pacific.
The Tsugaru Strait is an international strait which is open to foreign ships, including military vessels.
"No violation of territorial waters has taken place, and no international rule has been ignored," a Defense Ministry spokesperson said.
Russia and China held joint naval drills in the Sea of Japan as part of naval cooperation between the two countries from Oct. 14-17 involving warships and support vessels from Russia's Pacific Fleet.
Moscow and Beijing have cultivated closer military and diplomatic ties in recent years at a time when their relations with the West have soured.