BEIJING - The Chinese Foreign Ministry on Friday confirmed the same day's routine patrol by Chinese maritime surveillance vessels in the territorial sea off the Diaoyu Islands.

It is "normal activity" for the Chinese vessels to exercise China's jurisdiction over the waters, said ministry spokesman Hong Lei at a daily press briefing when responding to a question on the subject.

The Chinese side has performed this patrol since the Japanese government announced its "purchase" of the Diaoyu Islands in September, a move which constituted a grave violation of China's territorial sovereignty.