The Japanese Defense Ministry says a Chinese naval vessel sailed inside Japan's territorial waters off the southwestern prefecture of Kagoshima for around three hours on Wednesday.

The ministry says the Maritime Self-Defense Force spotted a Chinese Navy survey ship heading northeast in the contiguous zone west of Gajajima Island at around 7:50 p.m. on Tuesday.

The ship then entered Japan's territorial waters southwest of Kuchinoerabujima Island at around 0:10 a.m. on Wednesday. It left Japan's territorial waters south of Yakushima Island about three hours later and headed southeast.

This is the fourth time this year that a Chinese naval survey ship has sailed inside Japan's territorial waters.

The Japanese government used diplomatic channels to convey its concerns to China.

Chinese naval vessels have entered Japanese territorial waters a total of eight times.

The Defense Ministry says it is closely monitoring the activities of Chinese vessels and analyzing the reasons for their intrusions.