The United States government is hacking Chinese mobile phone companies to gather data from millions of text messages, former intelligence technician Edward Snowden told the Sunday Morning Post in Hong Kong. US spies have also hacked China's prestigious Tsinghua University in Beijing and Asia Pacific fibre-optic network operator Pacnet, the Post quoted Mr Snowden as saying.

Mr Snowden, who worked as a contractor for the National Security Agency (NSA), has been charged with espionage by the US after revealing a massive spying program and has gone to ground after fleeing to Hong Kong.

The Post said Mr Snowden had provided documents listing operational details of specific attacks on computers, including internet protocal (IP) addresses, over a four-year period.

Government data shows almost 900 billion text messages were exchanged in China in 2012.