A former contractor for the United States National Security Agency (NSA), charged by the United States with espionage, has been allowed to leave Hong Kong because a US extradition request did not fully comply with the law.

Edward Snowden left for Moscow and the South China Morning Post reports his final destination may be Ecuador or Iceland.

US authorities have charged Mr Snowden with theft of US government property, unauthorized communication of national defence information and wilful communication of classified communications intelligence to an unauthorized person.

Reuters reports the United States had asked Hong Kong, a special administrative region of China, to send him home.

But the Hong Kong government said that the documents provided by the US government did not fully comply with the legal requirements under Hong Kong law, there was no legal basis to restrict Mr Snowden from leaving Hong Kong.

Documents previously leaked by Edward Snowden revealed that the NSA has access to vast amounts of internet data such as emails, chat rooms and video from large companies, including Facebook and Google, under a government programme known as Prism.