China has deployed fighter jets to the same contested island on the South China Sea and has also sent surface-to-air missiles, US officials said on Tuesday.
Citing two unnamed US officials, Fox News said US intelligence services had spotted Chinese Shenyang J-11 and Xian JH-7 warplanes on Woody Island in the disputed Paracel Islands chain over the past few days.
Navy Captain Darryn James, a spokesman for US Pacific Command, confirmed the report but noted that Chinese fighter jets have previously used the island.
Woody Island, which is also claimed by Taiwan and Vietnam, has had an operational airfield since the 1990s but it was upgraded last year to accommodate the J-11.
"We are still concerned that the Chinese continue to put advanced arms systems on this disputed territory," James said.
Images released on Feb. 16 by civilian satellite company ImageSat International revealed that two batteries of eight surface-to-air missile launchers as well as radar targeting arrays had been deployed to Woody Island.
China confirmed that it had placed “weapons” on the island, defending what it said was its sovereign right to do so.
The latest deployment was reported after US Secretary of State John Kerry said that the militarisation of facilities in the South China Sea does not help resolve maritime claims there, ahead of his meeting with Chinese Foreign Minister Wang Yi.
Earlier in this week, the Chinese Foreign Ministry stated that the country’s deployment in the South China Sea is not different from US deployments in Hawaii, adding that there will not be a backdown of military deployments.
China has controlled all of the Paracels, which are also claimed by Vietnam and Taiwan, since the mid-1970s after the end of the Vietnam War.
But tensions in the sea -- through which one-third of the world's oil passes -- have mounted in recent months since China transformed contested reefs on the Spratly Islands into artificial islands capable of supporting military facilities.