Japan has expressed concern over China’s establishment of an “air defense identification zone” on Saturday that includes the disputed Diaoyu Islands in the East China Sea, Financial Times reported, citing a statement made by the Japanese foreign ministry. The Japanese foreign ministry lodged an immediate protest with the Chinese embassy in Tokyo, saying it was a “very dangerous” action. In an early test of China’s new zone, the Chinese air force sent early warning aircraft and fighter jets on a sweep of the area later in the day. The islands are know as Senkaku in Japan.