China is believed to have installed anti-aircraft and anti-missile weapons on its man-made islands in the strategically vital South China Sea, according to an analysis of satellite images by a US think-tank.
The Center for Strategic and International Studies said in a report late on Wednesday that the anti-aircraft guns and close-in weapons systems designed to guard against missile attack have been placed on all seven of China's newly created islands.
The outposts were built in recent years by piling sand on top of coral reefs followed by the construction of military grade 3,000-meter (10,000-foot) airstrips, barracks, lighthouses radar stations and other infrastructure.
CSIS based its conclusions on satellite images taken of the islands in mid-to-late November and published on the website of its Asia Maritime Transparency Initiative.
China's new island armaments "show that Beijing is serious about defense of its artificial islands in case of an armed contingency in the South China Sea," CSIS experts wrote in the report.
"Among other things, they would be the last line of defense against cruise missiles launched by the United States or others against these soon-to-be-operational air bases," the report said.
China's defense ministry did not immediately respond Thursday to a faxed request for comment. Beijing says the manufactured islands are intended to boost maritime safety in the region while downplaying their military utility. They also mark China's claim to ownership of practically the entire South China Sea, its islands, reefs and other maritime features.
Taiwan, Vietnam, the Philippines, Malaysia and Brunei also claim territory in the waterway through which an estimated $5 trillion in global trade passes each year, while the US Navy insists on its right to operate throughout the area, including in waters close to China's new outposts. China has strongly criticized such missions, formally termed Freedom of Navigation Operations.
The US has committed to beefing up its military presence in the area, although new uncertainty has been introduced by incoming president Donald Trump who broke long-established diplomatic protocol by talking on the phone earlier this month with the president of China's longtime rival Taiwan.
Trump has called for a reconsideration of its commitments to its Asian allies, including Japan and South Korea, while simultaneously criticizing Chinese trade policy toward the US along with its new territorial assertiveness.
Trump referred to China's man-made islands in a tweet earlier this month, saying Beijing didn't ask the US if it was OK to "build a massive military complex in the South China Sea."
"The timing is significant in that these first clear images come amid Trump's challenging comments about China and its South China Sea fortresses," said Alexander Neill, a senior fellow for Asia-Pacific security for the International Institute for Strategic Studies based in Singapore.
In all, China has reclaimed more than 1,295 hectares (3,200 acres) of land in the southeastern South China Sea. The US says the building doesn't give China any additional territorial rights and an international arbitration panel in the Hague ruled over the summer against China's historical claim to ownership of waters within the South China Sea. Beijing has ignored the ruling.
China has sought to emphasize the usefulness of the island developments for civilian navigation in the area, while also asserting its right to equip them with whatever means deemed necessary for their defense. Chinese President Xi Jinping said on a visit to the US last year that "China does not intend to pursue militarization" of the area, prompting some foreign experts to accuse China of going back on its word with its new deployments.
Despite that, China considers it vital to equip the islands with defensive means given their distance - 1,600 kilometers (1,000 miles) - from the Chinese mainland, together with the nearby presence of forces from rival claimants such as Vietnam, said Yue Gang, a retired colonel and military analyst.
"As the matter of fact, these occupied islands have been armed and fortified for a long time," Yue said. "No country in the world would only commit to providing civil services without considering its own security safety."
Hoping to avoid an armed naval conflict, China has thus far used its coast guard and law enforcement vessels to assert its claims and protect its interests. However, military spokesmen say they see a role in the region for the navy's sole operating aircraft carrier, along with similar vessels coming on line in the next few years.
Looking forward, the nature of China's new military deployments will likely be calibrated in response to moves taken by the US, said the IISS's Neill.
Augmenting its renewed emphasis on Asian security - referred to as the "pivot" by policymakers in Washington - the US could heighten the pace of naval operations in the area, including the use of undersea drones, and deploy advanced F-22 fighters to ally Australia, which sits on the region's southern rim.
China, in response, might dispatch submarines on regular patrols in the South China Sea while also siting surface-to-air missile batteries on the islands that it already maintains on the Paracel island group that it control located to the west.
"China will argue that they are entitled to place whatever they want there in reaction to US actions," Neill said. "The big question is whether Trump will embark on a more strident or discordant policy in the South China Sea."
(With inputs form AP)