Six Russian ships, including three navy warships, have passed through the Tsushima Strait in southwestern Japan as they traveled north from the East China Sea to the Sea of Japan, the Defense Ministry said Wednesday.
The ministry also confirmed that a Chinese navy reconnaissance vessel sailed from the East China Sea to the Pacific on Wednesday after traveling near Amami-Oshima Island in southwestern Japan.
The ministry is maintaining vigilance over what officials see as increasingly active movements of Chinese and Russian vessels around the Japanese archipelago.
The Maritime Self-Defense Force spotted the Russian ships around 9 a.m. on Tuesday about 80 kilometers west of the Danjo Islands before passing through the Tsushima Strait, located between Kyushu, one of Japan's four main islands, and South Korea.
The three Russian navy ships, including a destroyer, accompanied three vessels affiliated with Russian energy giant Gazprom PJSC, according to the ministry.
"It is rare for Russian private vessels to sail together with warships," a Defense Ministry's Joint Staff official said.
One of the commercial ships was the Akademik Cherskiy, a pipe-laying vessel that played a part in completion last year of the Nord Stream 2, a project initially designed to ship Russia's natural gas to Germany.
The project, however, was suspended in the wake of Russia's invasion of Ukraine.