According to Tokyo, from 03:15-03:22 a.m. on Wednesday (18:15-18:22 GMT on Tuesday), three ships of the Chinese coast guard entered Japan's territorial waters near the disputed islands, known as the Senkaku Islands in Japan and the Diaoyu Islands in China. The vessels tried to approach the Japanese fishing boats. The Japan Coast Guard called on the Chinese ships to leave the territorial waters and stay away from the fishing boats, according to Isozaki.
"Such activity of China Coast Guard’s vessels is a violation of international law. In this regard, we lodged a strong protest through diplomatic channels and called for the immediate withdrawal of the ships," the official said at a press conference.
Isozaki added that the appearance of Chinese vessels in the area was "unacceptable" and "extremely regrettable."
This is already the 27th such incident since the beginning of the year.
Another three Chinese ships were seen sailing in the adjacent zone, which closely borders Japan’s territorial waters. Two of them are equipped with autocannons, according to Japanese news agency Kyodo.
Both Japan and China have extended territorial claims over the Senkaku Islands. Japan insists on its sovereignty over the islands effective since 1895, while China points to the 1783 and 1785 Japanese maps designating the islands as Chinese territory. After World War II, the Senkaku Islands went under the control of the United States and were passed on to Japan in 1972.
Japan believes that China's sovereignty claims over the islands follow the discovery of valuable minerals in their shelf waters in the 1970s. The territorial dispute escalated in 2012, when the Japanese government purchased three of the five islands from a private owner, thereby confirming Japan's affiliation with the islands.