Taiwan has conducted a natural gas and oil survey in the disputed Spratly Islands, a legislator said Wednesday, the latest in a string of moves that risk stoking tensions over the South China Sea archipelago.

A team of technicians from the state-run CPC Corporation, Taiwan sailed to Taiping, the island in the chain that is controlled by Taipei, on Monday, legislator Lin Yu-fang's office said in a statement.

"They completed the survey on Tuesday afternoon and were on their way back to Taiwan escorted by a naval fleet" composed of a dock landing ship and a frigate, the statement said.

Taiwan risks ratcheting up regional tensions over the Spratlys with the move. The islands are also claimed entirely or in part by Brunei, China, Malaysia, the Philippines and Vietnam.

All the claimants except Brunei have troops based on the group of more than 100 islets, reefs and atolls, which are spread across a vast area but have a total land mass of less than five square kilometres (two square miles).

A senior assistant to Lin told AFP the step is expected to be followed by more sensitive surveys of the water in the vicinity, declining to provide details.

The geological survey came after the Taiwanese government granted the company permission in 2011 to explore for oil and natural gas in the waters off Taiping.

Taiwan maintains a small coastguard garrison on Taiping, 1,400 kilometres (870 miles) from its southern coast, and earlier this year sent new mortar and anti-aircraft systems to the islet, angering Vietnam.

Taipei also said it plans to build a dock big enough for warships in the disputed archipelago, an upgrade from the existing pier that caters only to small patrol boats.

Taiwan built a 1,150-metre (3,800-foot) runway on Taiping in mid-2006, despite protests from other countries.

The Philippines and Vietnam have been strengthening their military deployment in the area after complaining that China is becoming increasingly aggressive in asserting its own claims.