China secretly installs cruise missiles on South China Sea outposts

But a USA defense official told CNN it was unclear if the missiles remained on the outposts following the April exercises.

Asian countries including Vietnam and Taiwan have rival claims over the Spratlys.

She said any action to unilaterally militarise artificial islands in the South China Sea would go against that responsibility.

"(It's) very important for us to be present and the recent ship visits that I mentioned are directly relevant to the situation we have in the South China Sea...

"There will be near-term and long-term consequences, and we'll certainly keep you up to date", she added.

Sources told CNBC that over the past month Chinese military personnel had moved the missiles to Fiery Cross Reef, Subi Reef and Mischief Reef in the Spratly Islands.

"China's activities in the South China Sea is to uphold our sovereignty and territorial integrity".

China's Defense Ministry did not immediately respond to a request for comment on the latest report. "Anyone with no invasive intention will find no reason to worry about this".

The drill was held amid frequent forays made by United States naval and aircraft into the South China Sea to assert the freedom of navigation especially around the artificial islands built by China, where it has also established garrisons.

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Washington warned that Beijing would face unspecified "consequences" over its militarisation of the South China Sea, and said it had raised the issue with China. "And the US Navy has been the guarantor of that", Chief Pentagon Spokesperson Dana White told reporters.

She said the Chinese must understand that "they can not, and should not, be hostile, and understand that the Pacific is - is a place in which much commerce goes through". Dispute the controversy, China has been carrying land-reclamation efforts, building artificial reefs and has established air bases, radar and communication systems, naval facilities and defensive weaponry.

Earlier media reported about the plans of China to open a new military base overseas, like "Bagnet".

The US often sends warships near the islands to publicly challenge Chinese claims.

Hanging over everything was a massive display of Chinese military might in the sea on April 12, culminating in a parade led by Beijing's only aircraft carrier and personally reviewed by President Xi Jinping. China has to realise that they've benefited from the free navigation of the sea.

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

Julie Bishop, the foreign minister of USA ally Australia, said the reports, if accurate, would be a concern as the actions would be contrary to China's stated aspiration not to militarize the features.

"The only thing lacking are the deployed forces".

  • Adam Floyd