US PRISM programme leaker, Edward Snowden, has claimed that the National Security Agency (NSA) hacked China’s three state-run telecom firms to snoop on SMS data from the Chinese carriers.

Snowden is said to have provided confidential documents that reveals extensive attacks on China Mobile, China Telecom and China Unicom, according to the South China Morning Post.

Reports suggest that the three have a collective subscriber base of over one billion.

The surrendered data also revealed that NSA was responsible for attacks on Tsinghua University’s server and accessed computers at the Hong Kong headquarters of Pacnet, which runs a major network across the Asia Pacific region.

The latest disclosure follows after Snowden was formally charged by the US with espionage, setting in motion his extradition from Hong Kong.

Earlier, the Hong Kong authorities had been asked to arrest Snowden, charged with spying for disclosing a secret government electronic-surveillance programme, while the exile request is being finalised.

The latest hacking allegations are anticipated to strain relations with China as both the side trade charges against each other on cyber attacks.

Earlier, the UK had denied allegations that the intelligence agency Government Communications Headquarters (GCHQ) had breached the law over US Internet monitoring programme, Prism.

The Prism programme is reported to allow GCHQ to avoid formal legal processes necessary to obtain personal material including emails, photographs and videos, from major internet firms globally.