Washington DC, Sat Jun 22, 2013 - The United States has filed espionage charges against Edward Snowden, a former US National Security Agency contractor who admitted revealing secret surveillance programs to media outlets, according to a court document made public on Friday.

The charges are the government's first step in what could be a long legal battle to return Snowden from Hong Kong, where he is believed to be in hiding, and try him in a US court. A Hong Kong newspaper said he was under police protection, but the territory's authorities declined to comment.

Snowden was charged with theft of government property, unauthorized communication of national defense information and willful communication of classified communications intelligence to an unauthorized person, said the criminal complaint, which was dated June 14.

The latter two offenses fall under the US Espionage Act and carry penalties of fines and up to 10 years in prison.

A single page of the complaint was unsealed on Friday. An accompanying affidavit remained under seal.

Two US sources, speaking on condition of anonymity, said the United States was preparing to seek Snowden's extradition from Hong Kong, which is part of China but has wide-ranging autonomy, including an independent judiciary.

The Washington Post, which first reported the criminal complaint earlier on Friday, said the United States had asked Hong Kong to detain Snowden on a provisional arrest warrant.

Hong Kong's Chinese-language Apple Daily quoted police sources as saying that anti-terrorism officers had contacted Snowden, arranged a safe house for him and provided protection.

The report said the police had checked his documents but had not discussed other matters or taken any statements.

Hong Kong Police Commissioner Andy Tsang declined to comment other than to say Hong Kong would deal with the case in accordance with the law.

Snowden earlier this month admitted leaking secrets about classified U.S. surveillance programs, creating a public uproar. Supporters say he is a whistleblower, while critics call him a criminal and perhaps even a traitor.

He disclosed documents detailing US telephone and Internet surveillance efforts to the Washington Post and Britain's Guardian newspaper.

The criminal complaint was filed in the Eastern District of Virginia, where Snowden's former employer, Booz Allen Hamilton, is located.

That judicial district has seen a number of high-profile prosecutions, including the spy case against former FBI agent Robert Hanssen and the case of al Qaeda operative Zacarias Moussaoui. Both were convicted.

'ACTIVE EXTRADITION RELATIONSHIP'

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

They also showed that the government had worked through the secret Foreign Intelligence Surveillance Court to gather so-called metadata - such as the time, duration and telephone numbers called - on all calls carried by service providers such as Verizon.

President Barack Obama and his intelligence chiefs have vigorously defended the programs, saying they are regulated by law and that Congress was notified. They say the programs have been used to thwart militant plots and do not target Americans' personal lives.

US federal prosecutors, by filing a criminal complaint, lay claim to a legal basis to make an extradition request of the authorities in Hong Kong, the Post reported. The prosecutors now have 60 days to file an indictment and can then take steps to secure Snowden's extradition from Hong Kong for a criminal trial in the United States, the newspaper reported.

The United States and Hong Kong have "excellent cooperation" and as a result of agreements, "there is an active extradition relationship between Hong Kong and the United States," a US law enforcement official told Reuters.

Since the United States and Hong Kong signed an extradition treaty in 1998, scores of Americans have been sent back home to face trial. However, the process can take years, lawyers say.

Under Hong Kong's extradition process, a request would first go to Hong Kong's chief executive. A magistrate would issue a formal warrant for Snowden's arrest if the chief executive agrees the case should proceed.

Simon Young, a law professor at the University of Hong Kong, said the first charge of theft against Snowden might find an equivalent charge in Hong Kong, needed to allow extradition proceedings to move forward, but the unauthorized communication and willful communication charges may be sticking points that lead to litigation and dispute in the courts.

Whatever the Hong Kong courts decide could be vetoed by the territory's leader or Beijing on foreign affairs or defense grounds.

An Icelandic businessman linked to the anti-secrecy group WikiLeaks said on Thursday he had readied a private plane in China to fly Snowden to Iceland if Iceland's government would grant asylum.

Iceland refused on Friday to say whether it would grant asylum to Snowden.