Japanese defense officials say a Chinese naval survey ship has sailed in Japan's territorial waters off the southwestern prefecture of Kagoshima, following a similar entry in February.

The Defense Ministry says the Maritime Self-Defense Force spotted the ship traveling west in Japan's contiguous zone southeast of Yakushima Island at around 7:30 a.m. on Thursday.

The ministry says the vessel entered Japan's territorial waters southwest of the island at around 10 a.m. and left the waters at around 1 p.m., heading west.

This is the eighth time since November 2021 and the second time this year that a Chinese naval survey ship has sailed in Japan's territorial waters around Yakushima.

International law allows vessels, including warships, to pass through the territorial waters of another state as long as they do not threaten the security and order of the coastal state.

Defense Ministry officials say Chinese survey ships may be collecting information on seabed geography, water depths and seawater temperatures for use in submarine operations.

The ministry has lodged a protest with China through diplomatic channels, saying naval ships have sailed in Japan's territorial waters frequently even though Japan has repeatedly conveyed concerns to Beijing.

The ministry plans to continue monitoring Chinese vessel activity.