Satellite imagery, passed to The Daily Telegraph, shows that a substantial harbour has been built which could house a score of nuclear ballistic missile submarines and a host of aircraft carriers.
In what will be a significant challenge to US Navy dominance and to countries ringing the South China Sea, one photograph shows China’s latest 094 nuclear submarine at the base just a few hundred miles from its neighbours.
Other images show numerous warships moored to long jettys and a network of underground tunnels at the Sanya base on the southern tip of Hainan island.
Of even greater concern to the Pentagon are massive tunnel entrances, estimated to be 60ft high, built into hillsides around the base. Sources fear they could lead to caverns capable of hiding up to 20 nuclear submarines from spy satellites.
The US Department of Defence has estimated that China will have five 094 nuclear submarines operational by 2010 with each capable of carrying 12 JL-2 nuclear missiles.
The images were obtained by Janes Intelligence Review after the periodical was given access to imagery from the commercial satellite company DigitalGlobe.
Analysts for the respected military magazine suggest that the base could be used for "expeditionary as well as defensive operations" and would allow the submarines to "break out to launch locations closer to the US".
It would now be "difficult to ignore" that China was building a major naval base where it could house its nuclear forces and increase it "strategic capability considerably further afield".
The development so close to the sea lanes vital to Asian economies "can only cause concern far beyond these straits".
Military analysts believe that China’s substantial build up of its forces is gaining pace put has remained hidden from the world in the build-up to the Olympics.
China has diverted much of its resources from the huge Peoples Liberation Army to the navy, air force and missile development.
An old Russian aircraft carrier, bought by Beijing for "leisure activities" has been picked over by naval architects who hope to "reverse engineer" the ship.
Within the next five to 10 years the People's Liberation Navy is expected to build up to six carriers which will also coincide with the Royal Navy’s construction of two major carriers.
The location of the base off Hainan will also give the submarines access to very deep water exceeding 5,000 metres within a few miles, making them even harder to detect.
Britain’s Trident submarines have to remain on the surface when they leave Faslane in north east Scotland and cannot dive to depth until outside the Irish Sea.
While it has been known that China might be developing an underground base at Sanya, the pictures provide the first proof of the base’s existence and the rapid progress made.
Two 950 metre piers and three smaller ones would be enough to accommodate two carrier strike groups or amphibious assault ships.
Christian Le Miere, editor for Jane's Intelligence Review, said the complex underlined Beijing’s plan “to assert tighter control over this region".
"This is a challenge to any hegemonic power, particularly the US which still remains dominant in the region."
So far China has offered no public explanation for its building at Sanya.
* Notícia publicada al Telegraph. Compartim aquest article per l'interés que té per totes aquelles persones que segueixen el creixement xinès que, com es pot veure, avança a pas ferm.