Four Chinese vessels entered the territorial waters surrounding the disputed East China Sea islands, Japan's Coast Guard said on Sunday.

The four coastguard vessels sailed into the waters near the disputed islets at approximately 10:30 am and departed about an hour and a half later after being asked to leave, according to Sputnik News.

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Japan and China have been locked in a territorial dispute over the uninhabited East China Sea islands, known as the Senkaku islands by Japan and claimed as Diaoyu by China, with both countries claiming the islands as their own.

This comes a week after Chinese President Xi Jinping told Japanese Prime Minister Shinzo Abe that both countries should "put aside disruptions" and Japan should "exercise caution" on territorial disputes when the two met at the G20 summit.

Japan has repeatedly protested that China is escalating tensions by regularly sending ships to the disputed islands in spite of several warnings from Tokyo. Last month, Japan's coast guard also released video footage showing several Chinese vessels approaching the Senkaku islands.

The latest incident comes at a time when tensions are high in the region after North Korea carried out its fifth and most powerful nuclear test on Friday (Sept. 9), infuriating its neighbors and the international community.

Japan, U.S. and South Korea are counting on China, which is one of North Korea's few allies, to convince Pyongyang to adhere to UN sanction resolutions.

Tokyo is boosting defence ties with Philippines and other Southeast Asian countries, some of which are involved in territorial disputes with Beijing over the South China Sea.

TagsJapan, china, East China Sea, Senkaku Islands, Japan coast guard, Diaoyu Islands, East China Sea dispute, South China Sea