China has secretly built a major underground nuclear submarine base that could threaten Asian countries and challenge American power in the region, British media reported on Friday.

Satellite imagery, passed to The Daily Telegraph, reportedly shows that a substantial harbour has been built, which could house a score of nuclear ballistic missile submarines and a host of aircraft carriers.

The daily reported that 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 jetties and a network of underground tunnels at the Sanya base on the southern tip of Hainan Island.

The images were reportedly obtained by the Jane's 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'.

The Daily Telegraph reported that military analysts believed China's substantial build up of its forces was gaining pace but has remained hidden from the world in the build-up to the Olympics [Images].

"China has diverted much of its resources from the huge Peoples Liberation Army to the navy, air force and missile development," the daily reported.

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, it added.

Christian Le Miere, editor for Jane's Intelligence Review, said the complex underlined Beijing's [Images] 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."