China’s biggest and most advanced aircraft carrier was spotted in the East China Sea on Thursday by Japan’s Self-Defense Forces, marking the first time the Fujian was sighted by Japan.

The ship was sailing about 200 kilometers northwest of a disputed cluster of islands called the Senkakus in Japan and Diaoyu in China. A Japanese P-3C aircraft spotted three vessels and gathered information, according to a statement released by the Joint Staff Office.

Chinese Navy spokesperson Leng Guowei said in a statement that the Fujian is currently on a cross-regional mission and sailed through the Taiwan Strait to conduct scientific research tests and training. He added that the mission is part of the carrier’s normal development process and not aimed at any specific target.