A Chinese Navy survey vessel on Sunday entered Japan's territorial waters near islands in Kagoshima Prefecture, the Defense Ministry said.
The latest such sighting of Chinese ships in the area was in December. In the latest incident, a survey vessel crossed into Japanese waters from southwest of Yakushima Island at around 2:30 a.m., the ministry said, marking the seventh entry by a Chinese survey ship into waters off Kagoshima since November 2021.
The Japanese government expressed concern about the ship's actions to Beijing through diplomatic channels, the ministry said. The vessel sailed out of the territorial waters near Kuchinoshima Island, about 50 kilometers southwest of Yakushima, at around 4:10 a.m.
Chinese ships have repeatedly entered Japan's territorial waters or sailed through adjacent areas, most notably near the Senkaku Islands, a group of East China Sea islets controlled by Japan but claimed by China, which it calls Diaoyu.
China's growing military presence in the South and East China seas has been a source of friction with some countries in the regions due to many having overlapping territorial claims.
Survey vessels are often used to conduct research, such as determining underwater topography for submarine navigation.