China disputes Japan's territorial claim over waters in the East China Sea.
The area is claimed by both China and Japan and has been a point of contention in bilateral relations. China calls the islands Diaoyu, while Japan calls them Senkaku.
BEIJING (Reuters) China's Foreign Ministry on Thursday rebuffed Japan's territorial claims over disputed waters in the East China Sea, calling the move a "serious violation" of Chinese sovereignty.
"Chinese coast guard vessels carrying out law enforcement on the ground, in accordance with the law, is a legitimate measure to safeguard Chinese sovereignty," spokesman Wang Wenbin told reporters at a regular press briefing.
Wang made the remarks in response to a question about the Japanese coast guard saying that Chinese coast guard vessels had violated Japanese territorial waters around the disputed islets in the East China Sea.
The area is claimed by both China and Japan and has been a point of contention in bilateral relations. China calls the islands Diaoyu, while Japan calls them Senkaku.
China's coast guard said on Wednesday it had entered the waters around the disputed islets in the East China Sea to counter what it called an incursion by Japanese ships into Chinese territorial waters.
Chinese Maritime Police spokesman Gan Yu said in a statement that coast guard vessels entered Diaoyu waters for a "normal rights protection patrol," calling it a "routine movement."