(VOVworld) - The Japanese Defense Ministry said on Saturday that a Chinese naval intelligence ship was detected off the Boso Peninsula in Chiba Prefecture several times from Wednesday to Saturday.

The vessel did not intrude into Japanese territorial waters, the ministry said, but added it is rare for a Chinese naval vessel to sail back and forth in that area near Tokyo.

Japan has conveyed to China through a diplomatic channel its concern over the incident, and the Defense Ministry has begun to investigate why the Chinese naval intelligence ship was sailing there.

In November, a Chinese naval intelligence ship sailed back and forth near the Japan-controlled Senkaku Islands. China claims the islands and calls them the Diaoyu.