Updated

Two Chinese ships entered waters around islands at the centre of a dispute with Japan on Thursday in the latest such incident at a time of frayed ties between the Asian powers.

The two Chinese coastguard vessels sailed into the 12-nautical-mile territorial waters around the Tokyo-controlled Senkaku islands -- which Beijing calls the Diaoyus -- early in the morning, the Japanese coastguard said.

Often-testy ties have soured dramatically since Tokyo's nationalisation of part of the chain a year ago, with frequent confrontations between official ships from both sides.

Japan annexed what it says were the unclaimed islands in 1895. It says China's assertion of ownership only came after the discovery of resources in the seabed at the close of the 1960s.

Beijing maintains that the islands have been its territory for hundreds of years and were illegally snatched by Tokyo at the start of an acquisitive drive across Asia that culminated in World War II.