China on Tuesday again requested Japan to stop causing new disturbances over the Diaoyu Islands and safeguard the overall interests of bilateral ties.

Foreign Ministry spokesman Hong Lei made the comment at a regular press briefing in response to a visit by a group of Japanese lawmakers to the islands.

It was reported that eight lawmakers from Tokyo set sail for the Diaoyu Islands on Monday. The mission is believed to be related to Tokyo metropolitan government's plan of purchasing the islands.

Hong reaffirmed that the Diaoyu Islands and affiliated islands have been China's inherent territory since ancient times, and China has undisputable sovereignty over them.

"Any unilateral actions by the Japanese side over the Diaoyu Islands is illegal and invalid," said Hong.

He said China has lodged solemn representations with the Japanese side, demanding the country stop causing new disturbances and maintain the overall interests of China-Japan relations through concrete actions.

It is the second time for Japanese lawmakers to visit the Diaoyu Islands this month. Six Japanese lawmakers from both the ruling and opposition parties viewed the islands on June 10.