BEIJING (AFP) - China is to carry out a geographical survey of islands in the East China Sea at the centre of a bitter dispute with Japan, the official Xinhua news agency said on Tuesday.

The survey of the Diaoyu islands was part of a programme to map China's "territorial islands and reefs", Xinhua said, citing a state geographical agency. They are known as the Senkaku in Japan, which controls them.

The survey was part of China's efforts to "safeguard its maritime rights and interests", Xinhua said, without giving a date for the exercise or making clear whether it would involve activities on land or be confined to the sea.

It quoted Mr Zhang Huifeng, an official with China's National Administration of Surveying, Mapping and Geoinformation, acknowledging that the mapping could encounter problems.

"There are some difficulties in landing on some islands to survey, and in surveying and mapping the surrounding sea area of the islands, because some countries infringed and occupied these islands of China," he said.

The maritime dispute, which has simmered off and on for years, intensified last year when the Japanese government nationalised islands in the small chain it did not already own, triggering anger and protests in China.

Both sides have scrambled fighter jets to the area in recent weeks in a further escalation, though no actual clashes have taken place.