TOKYO, Reuters – A group of 10 vessels representing Russia and China sailed across a strait separating Japan’s northern and main islands, according to the Japanese government. They were also closely monitoring such activity.

Japan was first to confirm the passage of Russian and Chinese vessels through the Tsugaru Strit that separates the Sea of Japan (and the Pacific)

Although the Strait of Hormuz is internationally recognized, Japan’s relations with China are strained by conflicts over small East China Sea islands. Tokyo also has a dispute over territory with Moscow.

Yoshihiko Itozaki, Deputy Chief Cabinet Secretary, stated that the government was closely monitoring Russian and Chinese naval vessels activities in Japan.

“We will do everything we can to continue our surveillance activities in the waters and airspace surrounding Japan.”

Japanese Defence Ministry spokesperson stated that the vessel’s passage did not violate Japanese territorial waters.

Russia and China organized joint naval drills on the Sea of Japan, as part of naval cooperation. They held the drills between Oct. 14-17.

In recent years, Moscow and Beijing developed closer diplomatic and military ties at a moment when relations with the West were deteriorating.