The debate over who owns a group of islands in the East China Sea came to a head again on Tuesday.
A fleet of Japanese boats carrying about 80 activists had sailed into the waters around the islands but were intercepted by a fleet of Chinese maritime ships.
The Japanese ships were escorted out of the area by the Japanese Coast guard.
Later, the Chinese Foreign Ministry spokesperson said China had lodged a stern protest over the quote 'illegal trouble making'.
Japanese and Chinese patrol ships have been playing a cat-and-mouse game near islands which have potentially huge oil and gas reserves.
