Japan berated China today for sending coast guard and fishing vessels to violate Japanese territorial waters in the East China Sea.

At around 1:30 P.M., Aug. 5, the 11th Regional Coast Guard Headquarters in Okinawa Prefecture spotted two Chinese coast guard vessels and six fishing trawlers in Japanese waters near the Senkaku Islands (Diaoyu Islands), uninhabited territories administered by Japan but claimed by China.

This is the first time that China has sent coast guard and fishing ships into disputed waters together. Japanese foreign ministry officials suggested that this may be a sign of increased Chinese assertiveness.

According to an official statement on the Ministry of Foreign Affairs of Japan website, Japanese Vice Foreign Minister Shinsuke Sugiyama summoned Chinese Ambassador to Japan Cheng Yonghua to protest against China’s recent actions. Japan also issued formal complaints to officials at the Chinese embassy in Tokyo and to other Chinese officials via its embassy in Beijing.

The Japanese foreign ministry told China that the entry of Chinese vessels into Japanese territorial waters around the Senkaku Islands are “infringements upon Japanese sovereignty and are completely unacceptable.”

This latest incursion into Japanese waters comes at a time when Sino-Japanese tension in the East China Sea is on the rise. In June, Japan protested against a Chinese warship, a frigate, that sailed near the Senkaku Islands, and on Tuesday, Japan raised serious concerns about China’s “unilateral demands” at sea in its latest defense white paper.

Japan has also issued several complaints about Chinese military flights near the disputed islands.

Despite Chinese complaints, China maintains that the disputed islands are indisputable parts of China’s territorial holdings. “Conducting patrols near the Diaoyu Islands is the right of Chinese law enforcement units, and Japan doesn’t have the right to say anything about it,” said a Global Times editorial earlier this week.

The U.S. military has significant presence on Japanese territory, but has of yet issued any statement regarding China’s incursion.

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