WASHINGTON (Reuters) - China has installed anti-ship cruise missiles and surface-to-air missile systems on three of its outposts in the South China Sea, U.S. news network CNBC reported on Wednesday, citing sources with direct knowledge of U.S. intelligence reports.

FILE PHOTO: Chinese dredging vessels are purportedly seen in the waters around Fiery Cross Reef in the disputed Spratly Islands in the South China Sea in this still image from video taken by a P-8A Poseidon surveillance aircraft provided by the United States Navy May 21, 2015. U.S. Navy/Handout via Reuters/File Photo

The installations, if confirmed, would mark the first Chinese missile deployments in the Spratly Islands, where several Asian countries including Vietnam and Taiwan have rival claims.

China has made no mention of any missile deployments but says its military facilities in the Spratlys are purely defensive, and that it can do what it likes on its own territory.

China’s Defense Ministry did not immediately respond to a request for comment on the latest report.

The foreign ministry said China has irrefutable sovereignty over the Spratly Islands and that its necessary defensive deployments were for national security needs and not aimed at any country.

“Those who do not intend to be aggressive have no need to be worried or scared,” ministry spokeswoman Hua Chunying told reporters in Beijing.

China “hopes relevant parties can objectively and calmly view this”, she added.

CNBC quoted unnamed sources as saying that according to U.S. intelligence assessments, the missiles were moved to Fiery Cross Reef, Subi Reef and Mischief Reef within the past 30 days.

The U.S. Defense Department, which opposes China’s installation of military facilities on outposts it has built up in the South China Sea, declined comment. “We don’t comment on matters of intelligence,” a spokesman said.

Greg Poling, a South China Sea expert at Washington’s Center for Strategic and International Studies think-tank, said deploying missiles on the outposts would be important.

“These would be the first missiles in the Spratlys, either surface to air, or anti-ship,” he said.

He added that such deployments were expected as China built missile shelters on the reefs last year and already deployed such missile systems on Woody Island further to the north.

Poling said it would be a major step on China’s road to dominating the South China Sea, a key global trade route.

“Before this, if you were one of the other claimants ... you knew that China was monitoring your every move. Now you will know that you’re operating inside Chinese missile range. That’s a pretty strong, if implicit, threat,” he said.

CNBC said the YJ-12B anti-ship cruise missiles allowed China to strike vessels within 295 nautical miles. It said the HQ-9B long-range, surface-to-air missiles could target aircraft, drones and cruise missiles within 160 nautical miles.

Last month, U.S. Admiral Philip Davidson, nominated to head U.S. Pacific Command, said China’s “forward operating bases” in the South China Sea appeared complete.

“The only thing lacking are the deployed forces,” he said. Once these were added, “China will be able to extend its influence thousands of miles to the south and project power deep into Oceania”.

Davidson said China could use the bases to challenge the U.S. regional presence, and “would easily overwhelm the military forces of any other South China Sea-claimants.

“China is now capable of controlling the South China Sea in all scenarios short of war with the United States,” he said.