Japan has summoned the Chinese ambassador after three Chinese fishery patrol boats approached a chain of disputed, resource-rich islands in the East China Sea, the BBC reported.
According to the Japanese coastguard, the boats entered Japanese waters around the islands – known as Senkaku in Japanese and Diaoyu in Chinese – early Wednesday.
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Japan said the boats left the area, after the crews initially refused to do so, telling the coastguard: "We are conducting official duty in Chinese waters. Do not interfere. Leave China's territorial waters."
Japan's Chief Cabinet Secretary, Osamu Fujimura, said Beijing's envoy had been summoned by the Japanese foreign minister, in protest, adding: "It is clear that historically and legally Senkaku is an inherent territory of Japan."
In response, the Xinhua news agency reported that the Chinese boats had been carrying out a "routine patrols," in accordance with Chinese law, aimed at "strengthening fisheries management" as the fishing season comes to a close.
The foreign ministers of Japan and China, in Cambodia for the Association of Southeast Asian Nations (ASEAN) forum, are due to meet to discuss the uninhabited islands, which are also claimed by Taiwan, Agence France Presse reported.
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The incident comes amid increasing tensions between China and Japan, after Tokyo last week announced it was looking to buy the islands, which may contain valuable mineral reserves, from their private Japanese owner.
China's Foreign Ministry spokesman, Liu Weimin, hit back at the announcement, warning that "China's holy territory is not up for sale to anyone."