China on Monday urged Japan to stop causing new troubles over the Diaoyu Islands as reports say dozens of Japanese including several lawmakers had landed on the islands.

"The Diaoyu Islands and their adjacent islets have been inherent parts of Chinese territory since ancient times, and China has indisputable sovereignty over them," Foreign Ministry spokesman Liu Weimin said at a press briefing.

"Any unilateral action by Japan involving the Diaoyu Islands is illegal and invalid," said the spokesman.

"The Chinese side has lodged solemn representations to the Japanese side," said the spokesman, "which demand the Japanese side stop making new troubles and play its due part to maintain the overall situation of the relations between China and Japan."