A satellite image of China's secret underground nuclear submarine base on Hainan Island in the South China Sea.
China has secretly built an underground nuclear submarine base in the South China Sea, posing a new threat to powers in the region — a development the Pentagon says it has known about for at least two years.
Satellite photos of the base obtained by FOX News show a large harbor and massive tunnels that defense experts say could shelter many nuclear subs.
The Defense Department has estimated that by 2010 China will have five operational 094-class nuclear submarines capable of carrying 12 nuclear missiles each, according to the Daily Telegraph.
According to the Defense Department, China has 57 attack submarines, but these satellite pictures suggest their 094-class nuclear submarine may already be available.
“It’s very significant to have further visual evidence of the kinds of military build-up that they’ve been engaged in for some time,” said Stephen Yates, a senior fellow at the American Foreign Policy Council.
Photos of the base were taken on November 28 by DigitalGlobe’s QuickBird satellite, and first appeared in the military journal Jane’s Intelligence Review.
The secret base, known as Sanya, is located on the southern tip of Hainan Island in the South China Sea. Defense experts say the harbor feeds into waters so deep that the submarines could launch without having to surface, making it difficult to detect them from the sky.
That may pose a threat to U.S. naval dominance in the region, and to the nations just hundreds of miles from Hainan’s shores.
“It really is a point of force projection out into the South China Sea, and the South China Sea is a very, very important waterway critical to energy security,” said Yates.
The Pentagon has known about the secret submarine base for more than two years. It first showed up in press reports in 2007 and was mentioned in the Defense Department’s report to Congress on China’s military power last year.
When Defense Secretary Robert Gates visited China last November, he was given a tour of the Forbidden City — but not given answers about China’s growing military budget, which increased officially by 17 percent last year, making it Asia’s fastest growing military.
Calls to the Chinese Embassy seeking comment on the revelation were not returned.
FOX News’ Jennifer Griffin contributed to this report.