Four Chinese government ships have entered Japan's territorial waters around the Senkaku Islands in the East China Sea.

The Japan Coast Guard says the vessels entered territorial waters near the islands of Minamikojima and Uotsurijima early Monday morning.

The vessels are reportedly navigating in waters a few kilometers away from Japanese fishing and survey ships.

The coast guard says it has dispatched patrol vessels to ensure the safety of the Japanese ships and to warn the Chinese vessels to leave Japan's territorial waters immediately.

The incident marks the second time this year that Chinese government ships have been spotted in Japan's territorial waters around the Senkaku Islands. The first occurred on January 10.

Japan controls the Senkaku Islands. China and Taiwan claim them. The Japanese government maintains the islands are an inherent part of Japan's territory, in terms of history and international law. It says there is no issue of sovereignty to be resolved over them.