Chinese fighter jets flew unusually close to Japanese military patrol planes over the weekend, Tokyo said, after two Chinese aircraft carriers were spotted operating simultaneously in the Pacific for the first time.

Tokyo has complained to Beijing after a Chinese fighter jet tailed a Japanese patrol aircraft over the weekend, flying as close as 45 meters from the aircraft, according to Japan’s Defense Ministry.

A Shenyang J-15 carrier-based fighter tailed a Japan Maritime Self-Defense Force P-3C patrol plane for 40 minutes Saturday morning and 80 minutes Sunday afternoon, coming within 150 feet of the Japanese aircraft during both incidents, the Ministry of Defense said in a news release Wednesday.