A US official confirmed that China has placed a surface-to-air missile system on a disputed island in the South China Sea, in a move likely to exacerbate tensions with other claimants and the US.

Hours earlier, Taiwan’s Ministry of National Defense said that China had positioned anti-aircraft missiles on Woody Island in the Paracel chain, which is occupied by China but also claimed by Taiwan and Vietnam.

The US official confirmed the missile system deployment on that island but said it is unclear whether the deployment is intended for the long-term.

The official was not authorised to discuss the information publicly and so spoke on condition of anonymity.

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Asked about the reported deployment, Secretary of State John Kerry voiced serious concern over increasing militarisation by Beijing in the South China Sea.

He said that contradicted a public assurance from Chinese President Xi Jinping when he visited the White House last September.

Kerry did not confirm the deployment in his brief comments, nor did the Defense Department. A Pentagon spokesman, Navy Commader Bill Urban, said he could not comment on a matter of intelligence.

The deployment follows China’s building of new islands by piling sand atop reefs and then adding airstrips and military installations.

The buildup is seen as part of Beijing’s efforts to claim virtually the entire disputed sea and its resources, which has prompted some of its wary neighbours to draw closer to the US.

In Beijing, Chinese Foreign Minister Wang Yi accused the media of hyping the issue and saying more attention should be paid to the “public goods and services” provided by China’s development of its maritime claims.

– AAP