Japan lodged a protest with Beijing on Saturday after about 230 Chinese vessels were spotted in waters near a group of disputed islets in the East China Sea, the Japanese government said.
More than 200 fishing boats, as well as six Chinese coast guard ships, were sailing in a contiguous zone near the Japanese-administered Senkaku Islands, Tokyo said.
The uninhabited islets are also claimed by China and Taiwan, where they are known as Diaoyu and Tiaoyutai, respectively.
“This is a unilateral act that raises tensions. It is unacceptable to us," Kenji Kanasugi, a Japanese foreign ministry official, told the Chinese Embassy in Japan.
Japan summoned the Chinese ambassador to Japan, Cheng Yonghua, to lodge a protest late Friday after a total of eight Chinese fishing vessels and coast guard ships entered what Tokyo regards as its territorial waters near the Senkakus.
China’s moves come after Japanese Prime Minister Shinzo Abe on Wednesday appointed Tomomi Inada as the country's new defence minister in a cabinet reshuffle. Inada has controversially denied Japan's Nanjing Massacre in 1937.