China took countermeasures on Wednesday morning against several Japanese ships that illegally entered China's territorial waters surrounding the Diaoyu Islands in the East China Sea, a coast guard official said.

China Coast Guard spokesman Gan Yu said in a news release that Chinese ships "used necessary control measures" when the Japanese vessels, some of which belong to the Japan Coast Guard, were found moving into waters near the Diaoyu Islands. He did not elaborate on details of the operations.

"We urge Japan to immediately cease all illegal activities in the waters around the Diaoyu Islands and its affiliated islets, which are inherent territories of China and are subject to our law enforcement activities," he said. "We call on the Japanese side to ensure that similar incidents do not happen again."