A new diplomatic row has flared between Japan and China over a remote chain of islands, after Beijing moved to assert an "indisputable sovereignty" over the uninhabited territories.
Three Chinese patrol boats approached the islands claimed by Japan in the East China Sea on Wednesday morning, prompting Japanese Foreign Minister Koichiro Gemba to formally complain to his Chinese counterpart during talks in Cambodia.
The crews of the vessels, which have since left the islands' immediate vicinity, initially rebuffed Japanese orders to leave.
It is the third time recently that China has clashed with its immediate neighbours over disputed territory and the row threatens to overshadow attempts to smooth regional relations at the security summit in Cambodia.
Responding to Japan's complaints, Chinese Foreign Minister Yang Jiechi countered to Gemba that the islands - known as Senkaku in Japanese and Diaoyu in Chinese - "have always been China's territory since ancient times, over which China has indisputable sovereignty". The move came ahead of a summit of the 10-member Association of Southeast Asian Nations (ASEAN) due to start in Cambodia on Thursday.
"ASEAN foreign ministers are having an emergency meeting to resolve the wording on the South China Sea in the joint statement," one Asian diplomat told AFP news agency on condition of anonymity on Wednesday.