Five Chinese naval ships entered the Sea of Japan heading in the direction of Russia over the weekend, Japan's Defense Ministry said, after Beijing announced joint military drills with Moscow.

The ministry "confirmed that these vessels sailed north-eastwards through the Tsushima Strait toward the Sea of Japan from Saturday to Sunday," it said in a press release on Monday.

Japan's Self-Defense Forces "conducted vigilance monitoring and intelligence gathering" with a vessel and patrol plane, the ministry said, releasing photos of the ships.