EXCLUSIVE: The U.S. intelligence community thinks the "hundreds" of surface-to-air missiles that China recently shipped to its Hainan Island in the South China Sea will be moved to the country’s nearby and disputed man-made islands in the coming months, two military officials told Fox News on Saturday.

The plan follows what U.S. intelligence officials say is Beijing’s expressed desire to protect its three airstrips on three of the man-made islands.

The missiles now on Hainan island, China’s largest in the South China Sea, are a combination of short- medium- and long-range weapons. And they include one battalion of the advanced SA-21 system, a long-range missle system that is based on fourth-generation Russian software and capable of knocking out aircraft from as far away as 250 miles.

The total number of surface-to-air missiles on Hainan could reach 500, one of the military officials told Fox News.

China shipping more surface-to-air missiles from the mainland to the South China Sea was first reported Friday by Fox News.

The new missiles have been seen by American intelligence satellites on China’s provincial island province of Hainan, which is not part the disputed islands.

Officials think the location is “only temporary” and likely a training site before the missiles are deployed in early 2017 to the contested Spratley Islands or Woody Island.

The two missile systems seen on Hainan island are known as the CSA-6b and HQ-9. The CSA-6b is a combined close-in missile system with a range of 10 miles and also contains anti-aircraft guns. The longer-range HQ-9 system has a range of 125 miles, and is roughly based on the Russian S-300 system.

This latest deployment of Chinese military equipment comes days after the Chinese returned an unclassified underwater research drone in the South China Sea. The Pentagon accused a Chinese Navy ship of stealing the drone, over the objections of the American crew operating it in international waters to collect oceanographic data.

The escalation comes weeks after President elect-Donald Trump received a congratulatory phone call from Taiwan’s president breaking decades-long “one-China” protocol and angering Beijing.

China has deployed surface-to-air missiles to Woody Island in the South China Sea before, as Fox News first reported in February.

It has yet to deploy missiles to its seven man-made islands in the Spratly chain of islands. Weeks ago, civilian satellite imagery obtained by a Washington, D.C., based think-tank showed gun emplacement on all the disputed islands, but not missiles.

Earlier this month, Fox News first reported China getting ready to deploy another missile defense system from a port in southeast China. China also flew a long-range bomber around the South China Sea for the first time since March 2015 and days after Mr. Trump’s phone call with his Taiwan counterpart.

Days before President Trump’s call, a pair of long-range H-6K bombers flew around the island of Taiwan for the first time.

Beijing has long expressed interest in fortifying its seven man-made islands in the South China Sea.

Last year, China’s President Xi Jinping pledged not to “militarize” the islands, in the Rose Garden at the White House.

“This another example of the adventurous and aggressiveness of the Chinese in the face of an anemic and feckless set of policies that we've seen over the last eight years,” said retired Air Force Lt. Gen. David Deptula, former head of Air Force intelligence, in an interview with Fox News.

This month, U.S. intelligence satellites also spotted components for the Chinese version of the SA-21 system at the port of Jieyang, in southeast China, where officials say China has made similar military shipments in the past to its islands in the South China Sea.

The Chinese SA-21 system is a more capable missile system than the HQ-9.

Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel. You can follow him on Twitter: @LucasFoxNews