China is to ramp up development on a disputed South China Sea island, a local government chief has said, in a move likely to stoke a growing territorial row with its neighbours.

The development of roads, water supply and drainage systems will be stepped-up in the new "capital" city of Sansha on Yongxing, one of the islands that make up the disputed Paracel chain, Luo Baoming, Communist Party secretary of southern Hainan Province told state television on Saturday.

Luo also said steps will also be taken to enforce China's "legal rights" in the region, which includes other island chains which are the subject of competing claims by Asian countries.

Beijing enraged Vietnam and caused concern in Washington when it announced the establishment of a new city and military garrison at Sansha in July.

The island, under the control of Hainan Province, will have administrative control over a region that encompasses not only the Paracels, but Macclesfield Bank, a largely sunken atoll to the east, and the Spratly Islands to the south.

The sovereignty of each remains a matter of dispute.

"To safeguard our legal rights in the South China Sea, we are now coordinating between the relevant departments in order to set a more unified, and efficient law enforcing body," Luo said.

Domestic media reported in August that work had begun on sewage disposal and waste collection facilities for the island's roughly 1,000 residents.

Beijing claims most of the South China Sea, which is home to vital shipping lanes and substantial proven and estimated oil and gas deposits.

Taiwan and ASEAN members the Philippines, Vietnam, Brunei and Malaysia all have rival claims on areas of the sea, while the United States is also watching China's increased assertiveness closely.

The announcement in July that Sansha would be established led to a formal protest being lodged by Vietnam, which said it violates international law.

The Philippines, which is involved in a dispute over the Spratly Islands, summoned the Chinese ambassador to lodge a complaint against the garrison announcement.