TOKYO (Kyodo) -- Japan said Thursday it has lodged a strong protest with China after Chinese coast guard ships entered Japanese territorial waters around the Senkaku Islands in the East China Sea and tried to approach a Japanese fishing boat operating there.

Chief Cabinet Secretary Yoshimasa Hayashi said the Chinese action violated international law, describing the ships' intrusion into Japanese waters as "unacceptable."

"We made a strong protest with China through a diplomatic channel and called for the ships to leave our country's territorial waters immediately," Hayashi told a press conference.

"The Senkaku Islands are undoubtedly Japan's inherent territory based on both history and international law," the top government spokesman said.

China has repeatedly sent ships to waters around the Senkaku Islands, uninhabited islets administered by Japan but claimed by China. The last time a Chinese vessel was confirmed to have entered Japan's waters was Nov. 8.

Two Chinese coast guard vessels entered Japanese territorial waters early Thursday, prompting Japan Coast Guard ships to be dispatched to ensure the safe navigation of the Japanese fishing boat, according to Hayashi.

The Chinese ships were equipped with what looked to be machine guns, the Japan Coast Guard said.