China said Thursday that its aircraft carrier Liaoning was on a routine training mission in the western Pacific, rejecting Tokyo’s accusation that the ship and its escorts had entered Japanese territorial waters.

In the latest incident in a long-running dispute between China and Tokyo over maritime activities, Japan’s Defense Ministry said on Wednesday that an aircraft carrier and two accompanying destroyers had sailed between the southern islands of Yonaguni and Iriomote in waters it controls.

The Ministry of Defense in China replied on Thursday and said that the court had conducted an exercise corresponding to related international law. It did not give the exact location of the fleet. “There is no need for the parties involved to over-interpret this,” the Defense Ministry said in a statement.

Japan’s Deputy Chief Cabinet Secretary, Moriya Yutaka, said on Wednesday that the incident was “completely unacceptable” and that the Japanese government had expressed serious concerns to the Chinese government. Japan will continue to closely monitor the activities of Chinese military vessels in adjacent waters, Moriya said.

Increased Chinese military activity near Japan and around the island of Taiwan has worried Tokyo in recent years. Japan has responded by beefing up its defenses, which it says are aimed at deterring China from using military force to advance its territorial claims in the region.

Last month, Japan lodged a protest with Beijing after a Chinese naval survey vessel entered Japanese territorial waters. He also accused the Chinese spy plane of violating his airspace.