Japan scrambled fighter jets Monday after an unidentified drone flew near the Japan-controlled islands at the center of a bitter dispute with China, a Defense Ministry spokesman said in the first reported incident of its kind.

The Air Self-Defense Force sent a number of jets to the Senkaku Islands area and the drones didn't enter Japanese airspace, the official said.

It was the second day in a row for Japan to scramble fighter jets as security is stepped up before the one-year anniversary Wednesday of the Japanese government's purchase of three of the uninhabited islets at the heart of its fraying ties with China.

China claims the islands as Diaoyu and Taiwan claims them as Tiaoyutai.

"Japan will enforce increased security to protect our land, sea, and airspace around the Senkaku Islands in the East China Sea," Chief Cabinet Secretary Yoshihide Suga said at a press conference.

The drone flew within the air defense identification zone, an area where airplanes must identify themselves and provide their intended flight routes and other information, the defense ministry said.

"I am not aware of the situation but want to emphasize that the Diaoyu Islands are an integral part of Chinese territory," Chinese Foreign Ministry spokesman Hong Lei said at a press conference.

On Sunday, two Chinese H-6 bombers flew round trip from the East China Sea to the Pacific Ocean without violating Japanese airspace the same day after overflying waters between Okinawa's islands, the Defense Ministry said Sunday. In response, the ASDF scrambled fighters. It was the first time the ministry has publicly confirmed the passage of Chinese bombers in that area.