The Japanese Government lodged a protest with the Chinese Embassy on Friday after four Chinese coast guard vessels entered what Japan says are its territorial waters, reports said.
A total of seven Chinese ships — including the four coast guard vessels — were spotted near the Japanese-administered Senkaku Islands, the Kyodo News agency reported, citing the Japan Coast Guard.
The islands are also claimed by China and Taiwan, which call them Diaoyu and Tiaoyutai respectively.
The Japan Coast Guard repeatedly urged the four ships to leave the waters, while one of them returned a similar warning in Chinese and Japanese, Kyodo said.
The incident came a day after Japan observed the 68th anniversary of its surrender in World War II.
Three cabinet ministers offered prayers at the controversial Yasukuni Shrine, which honours the nation’s 2.5 million war dead, including 14 Class A war criminals from World War II.
Prime Minister Shinzo Abe stayed away from the war memorial, but sent a ritual offering.
The ministers’ visit to the shrine sparked criticism from China, South Korea and Taiwan, which see it as glorifying Japan’s wartime aggression.