A Chinese navy ship sailed near the Japanese-administered Senkaku Islands early Thursday, prompting a formal diplomatic complaint from Tokyo, a news report said.
The Chinese frigate was spotted by a Japanese destroyer entering the contiguous zone north-east of Kuba Island in the East China Sea, before exiting around two and a half hours later, Kyodo News agency reported, citing the Japanese Defence Ministry.
Chinese coast guard vessels have been seen in Japan's contiguous zone before, but this was the first reported sail-past by a navy vessel, Kyodo reported.
According to the UN Convention on the Law of the Sea, a state's contiguous zone starts from the limits of its territorial waters, 12 nautical miles (22 kilometres) off shore, extending a further 12 nautical miles out to sea.
Within that band, the state can exert limited control to prevent various violations, but foreign vessels have the right to transit the waters without notification in a reasonable manner.
Chinese Ambassador Cheng Yonghua was summoned to the Japanese Foreign Ministry to receive a protest over the incident, Kyodo said.
Three Russian military vessels were also spotted in the contiguous zone around the same time, the report said, citing the Defence Ministry.
The ministry said the Chinese ship did not enter the territorial waters off the Senkaku, which are also claimed by China and Taiwan, where they are known as Diaoyu and Tiaoyutai, respectively.