By Li Hongmei

China will send a team at an "appropriate time" to survey the Diaoyu Islands at the heart of an increasingly heated dispute with Japan, a Chinese official said on the sidelines of the ongoing annual sessions of the National People's Congress (NPC) and the Chinese People's Political Consultative Conference (CPPCC).

Li Mingde, vice director of China's mapping agency, and also a member of the CPPCC, told CCTV on Sunday that surveying by land would allow the mapping of caves and other features not visible from the air.

"My hope is that we can get under way under conditions where the situation is relatively good and the survey team's physical safety can be assured," Li said.

The islands are the focus of a decades-long dispute that reignited in September, when the Japanese government "purchased" three of the islands from so-called private owners.

The purchase prompted anti-Japan protests in China, which has since regularly sent marine surveillance ships to patrol territorial waters around the islands.

China and Japan have accused one other of tailing each other's aircraft, and Japan last month said a Chinese ship locked its weapons fire control radar onto one of its ships. China denied the claim and accused Tokyo of seeking to escalate tensions.

China says it will continue stepped-up patrols indefinitely, in an apparent attempt to wear down the Japanese Coast Guard, and plans to use unmanned aircraft to patrol the islands.