Beijing has lodged solemn representation to Tokyo over Japanese local lawmakers' activities in the waters off Diaoyu Island, the Foreign Ministry said on Tuesday.

Reports said eight Tokyo Metropolitan Assembly members departed on Monday night to conduct a so-called "survey" in waters off Diaoyu Island.

"China has lodged solemn representations with Japan, demanding Japan to stop creating new disturbances and safeguard the overall interest of China-Japan relations with concrete actions," Foreign Ministry spokesman Hong Lei said at a daily news conference on Tuesday.

Hong reiterated that Diaoyu Island and its affiliated islands have been a part of China's inherent territory since ancient times, and China has indisputable sovereignty over them. "Any unilateral move taken by Japan over Diaoyu Island is illegal and invalid," he said.