Four Chinese warships entered Japanese territorial waters, and the Japanese government protested China's actions.

According to Voice of America, on June 7th, Japan objected to China's four armed coast guard vessels entering the territorial waters near the disputed Senkaku Islands (which China claims are the Diaoyu Islands) in the East Sea. The Japanese government said it had been confirmed that a Chinese ship armed with automatic weapons had entered Japanese waters for the first time.
Japanese Chief Cabinet Secretary Yoshimasa Hayashi said at a press conference on June 7: "I don't know what China's intentions are, but it is against international law for Chinese coast guard ships to invade our territory."
China's coast guard has claimed that its armed vessels are patrolling China's waters, and that such patrols are routine to protect maritime sovereignty, security, maritime rights, and interests.
According to Japan's Kyodo news agency, the Japanese Coast Guard said that after 10:30 a.m. local time last Friday, four armed vessels belonging to the Chinese Coast Guard entered the waters around the Senkaku Islands at the same time. After 10 minutes, he announced that he had entered the neighboring area.
According to reports, the contiguous area usually refers to the sea area extending about 22 kilometers from the sea surface of a country. Foreign military ships can enter the border area. Although it is not illegal for Chinese military vessels to sail through the area, the continued presence of Chinese military vessels in the border area is considered an act of provocation.
The Japanese Coast Guard said this is the first time since August 2016 that more than four Chinese ships armed with automatic weapons have entered Japan's territorial waters.