TOKYO (Kyodo) — A Chinese navy survey ship entered Japan’s territorial waters off its southwestern islands on Saturday, the Japanese Defense Ministry said, less than a week after Tokyo strongly protested a Chinese military aircraft’s airspace breach.

Japan again protested through diplomatic channels to China and conveyed its strong concern over the latest crossing, the ministry said. It marked the 10th entry by a Chinese survey ship into Japanese waters off Kagoshima Prefecture since November 2021.

The vessel was spotted entering the territorial waters west of Kuchinoerabu Island around 6 a.m. and left the waters southwest of Yakushima Island at around 7:53 a.m., the ministry said. The Maritime Self-Defense Force sent a minesweeper and patrol aircraft to monitor the Chinese vessel.

Survey vessels are often used to conduct research on underwater topography for submarine navigation.

The latest case comes after Japan on Monday confirmed for the first time that a Chinese military spy plane violated Japanese airspace over waters in the East China Sea off islands in the southwestern prefecture of Nagasaki.

In recent years, Chinese ships have also repeatedly entered Japan’s territorial waters in the East China Sea, around the Japanese-controlled Senkaku Islands, which China claims and calls Diaoyu.