BEIJING - China will begin civilian flights to and from a disputed South China Sea island within a year, state media reported on Friday, as the government expands infrastructure on islands and reefs also claimed by other countries in region.

The flights will be to Sansha city, on Woody Island in the Paracel archipelago, China's administrative base for islands and reefs it controls in the South China Sea.

China claims most of the energy-rich waters through which about $5 trillion in ship-borne trade passes every year. Neighbours Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims.

The United States has voiced concerns about China's assertive pursuit of territory in one of the world's busiest trade routes.

Two passenger ships and a police vessel are base stations for mobile communications in Sansha, the official Xinhua news agency reported, citing an interview with Mayor Xiao Jie.

The airfield in Sansha and a newer one on Fiery Cross Reef in the Spratly archipelago are expected to boost air traffic services in the region, Xiao added, aiding navigation and surveillance while providing weather and aeronautics information.

U.S. and Taiwan officials confirmed in February the "very recent" placement of surface-to-air missiles on Woody Island, the site of the largest Chinese presence on the Paracels, criticising the move as contrary to China's commitments not to militarise its claims in the South China Sea.

Beijing says it is entitled to "limited defensive facilities" on its territory, and dismissed reports about the missile placement as media hype. China says much of the infrastructure it is building is purely civilian in nature and will benefit other countries.

China landed fully-armed jet fighters on an expanded airstrip on Woody Island in November, and reinforced hangars have been completed, regional diplomats have told Reuters.