Japan's defense ministry announced on Monday that five Chinese naval vessels had entered the Sea of Japan. The announcement came as China revealed plans to soon hold military drills in the area with the participation of Russia.

The ministry said Japan's Maritime Self-Defense Force personnel spotted the Chinese flotilla of naval ships sailing northeastward in the East China Sea from Saturday through Sunday.

The group of vessels then entered the Sea of Japan, following a passage through the Tsushima Strait.

China's defense ministry said on Monday that the Russian military would participate in a military exercise it was planning to hold in the seas of Japan and Okhotsk in the near future.

Japanese defense ministry officials say the five Chinese naval ships might participate in the drills. The officials said they will keep an eye on their moves.