The South China Morning Post reported on Sunday that Snowden had left Hong Kong and was en route to Moscow on a commercial flight, heading to an unnamed third destination.

Russia's Interfax news agency, quoting an unidentified source at the Aeroflot airline, reported that there was a ticket in Snowden's name for a flight on Monday to Cuba, from where he was to fly to the Venezuelan capital Caracas.

The former NSA employee allegedly revealed the existence of the spy program Prism, which surveils phone and online activity.

Watch video 00:30 Snowden leaves Hong Kong

In a statement posted online Sunday, the Hong Kong government confirmed Snowden "left Hong Kong today on his own accord for a third country through a lawful and normal channel" and that it had informed the US of Snowden's departure.

The WikiLeaks website has tweeted: "WikiLeaks has assisted Mr. Snowden's political asylum in a democratic country, travel papers ans [sic] safe exit from Hong Kong." It said Snowden was accompanied by WikiLeaks' legal advisors.

A day after making public espionage charges filed against Snowden, US officials confirmed they had asked authorities in Hong Kong for his extradition. The 30-year-old former NSA employee is believed to have fled there in early June.

In Sunday's statement, the Hong Kong government said that because the US request did not fully comply with Hong Kong law, it had asked for more information to analyze whether the request could be fulfilled.

Earlier, prosecutors reportedly delayed the request in order to ensure the charges sufficiently complied with Hong Kong's terms for deporting a wanted US citizen.

"Hong Kong has been a historically good partner of the United States in law enforcement matters, and we expect them to comply with the treaty in this case," White House national security adviser Tom Donilon said in an interview with the US television broadcaster CBS. He said the US presented Hong Kong with a "good case for extradition."

On Friday, US prosecutors published the criminal complaint against Snowden, dated June 14. The charges were filed in the eastern district of the US state of Virginia, where his former employer, Booz Allen Hamilton, is based.

The former contractor faces charges that could lead to a maximum sentence of 10 years in prison: unauthorized communication of national defense information, willful communication of classified information and theft of government property. The first two charges fall under the Espionage Act.

Snowden: US hacking China

According to an online article in the South China Morning Post published Saturday, Snowden has leaked information about US espionage in China.

In a June 12 interview, Snowden reportedly told the Post that the US had hacked into Chinese mobile phone companies, as well as into the Hong Kong headquarters of Pacnet, which owns "the most extensive fiber optic submarine cable networks in the region." He also contended that as recently as Jauary the US had hacked into the databases of Tsinghua University, one of China's top institutions for higher education.

The former NSA employee showed the Post documents to support his claims, according to the article.

Washington and Beijing have issued several warnings against each other for alleged cyberespionage over the past year. The US has maintained innocence in the rows, pointing the finger instead at China for attempting to mine information illegally.

A report published earlier this month by the UK newspaper the Guardian revealed the existence of a surveillance program known as Prism, which surreptitiously gathers intelligence from phone and Internet records. Snowden claimed responsibility for leaking the information several days later.

Despite attempts to reassure the public that the government cannot gather information without a court order - comparable to a search warrant obtained with evidence of probable cause - the NSA and the administration of US President Barack Obama have faced sharp criticism from the public since the article appeared. The president continues to defend the program as a necessary measure for US security.

NSA officials have said the program helped authorities deter 50 "potential terrorist events" since the September 11, 2001, attacks.

kms, jr/mkg (AP, AFP, Reuters, dpa)