Japan's Defense Ministry says six vessels from the Russian and Chinese navies fired machine guns in the Sea of Japan. It suspects the act to be part of major Russian military drills.
The ministry says Japan's Maritime Self-Defense Force confirmed that three Russian frigates and three Chinese ships were sailing east in waters about 190 kilometers west of Cape Kamui in Japan's northernmost prefecture of Hokkaido on Saturday afternoon. It says the Chinese vessels included a destroyer.
The ministry says the six vessels fired machine guns in waters near where they were spotted. It adds that the ships later navigated through the Soya Strait and entered the Sea of Okhotsk.
Russia on Thursday launched a weeklong exercise called Vostok in the Sea of Japan and other areas. It involves forces from China and other countries.
Japan's Defense Ministry is continuing surveillance and monitoring.