MOSCOW (AFP) - Former United States spy Edward Snowden on Sunday arrived in Russia from Hong Kong, reportedly on his way to Venezuela, escaping the clutches of US justice at least for now, in a shock development sure to infuriate Washington.

Snowden, the target of a US arrest warrant issued on Friday after he blew the lid on massive secret surveillance programmes, arrived in Moscow on a direct flight operated by Russian flag carrier Aeroflot.

The Hong Kong government said earlier it had "no legal basis" to prevent Snowden leaving because the US government had failed to provide enough information to justify its provisional arrest warrant for the former National Security Agency (NSA) contractor.

Snowden, 30, landed at Sheremetyevo airport in the north of Moscow at 5.05pm (9.05pm Singapore time), but there was no immediate official confirmation of where he would head next, an Agence France-Presse correspondent at the airport said.

Russian media reports citing sources within Aeroflot said he would fly to Cuba on Monday and then board a flight to the Venezuelan capital Caracas.

"Russian law enforcement agencies have nothing against him and we have no orders to detain him," one law enforcement source told the state news agency Ria Novosti.

Relations between Russia and the US remain frosty because of discord over a raft of issues including the Syria conflict, reflected in a tense meeting between Presidents Barack Obama and Vladimir Putin at the G-8 summit in Northern Ireland last week.

Julian Assange's WikiLeaks operation claimed credit for helping to arrange asylum for the man behind one of the most significant security breaches in US history.

"Mr Edward Snowden, the American whistleblower who exposed evidence of a global surveillance regime conducted by US and UK intelligence agencies, has left Hong Kong legally," WikiLeaks said in a statement.

"He is bound for a democratic nation via a safe route for the purposes of asylum, and is being escorted by diplomats and legal advisors from WikiLeaks," it said, without revealing his final destination.

Snowden's latest interview on Sunday contained new revelations about US cyber-espionage against Chinese targets, drawing a stinging response from China's official news agency, which branded Washington an espionage "villain".

The South China Morning Post, which has carried exclusive interviews with Snowden in Hong Kong, said Moscow would not be his final destination, and suggested that Iceland or Ecuador - which is currently giving Assange asylum in its London embassy - may be his ultimate port of call.

Snowden abandoned his high-paying job in Hawaii and went to Hong Kong on May 20 to begin issuing a series of leaks on NSA eavesdropping of phones and computer systems, triggering concern from governments around the world.

Obama's administration has insisted on the legality of the vast surveillance programme and said it has foiled a number of extremist plots.

Snowden's departure from Chinese territory could result in US retaliation against Hong Kong, but more broadly the affair is a shock to the Obama administration, which on Friday unveiled charges including theft and espionage against him.

White House National Security Advisor Tom Donilon had said on Saturday that the charges presented a "good case" for Hong Kong to extradite him and that "we expect them to comply with the treaty in this case".

The government of Hong Kong, a special administrative region (SAR) under Chinese rule that has maintained its own British-derived legal system, said it had informed Washington of Snowden's exit after determining that the documents provided by the US government did not fully comply with Hong Kong legal requirements.

"As the HKSAR government has yet to have sufficient information to process the request for provisional warrant of arrest, there is no legal basis to restrict Mr Snowden from leaving Hong Kong," it said in a statement.

It also pressed Washington for answers "on earlier reports about the hacking of computer systems in Hong Kong by US government agencies".

China's official Xinhua news agency attacked the US as an espionage "villain" after Snowden detailed new allegations of NSA activity
targeting mainland and Hong Kong interests.

In the latest revelations in the South China Morning Post, Snowden said the NSA was hacking Chinese mobile phone companies to gather data from millions of text messages.

He said US spies have also hacked the prestigious Tsinghua University in Beijing - home to one of six "network backbones" that route all of mainland China's Internet traffic - and the Hong Kong headquarters of Pacnet, which operates one of the Asia-Pacific region's largest fibre-optic networks.

"These, along with previous allegations, are clearly troubling signs," Xinhua said in a commentary. "They demonstrate that the United States, which has long been trying to play innocent as a victim of cyber attacks, has turned out to be the biggest villain in our age.

Snowden's claims about Pacnet followed a report in Britain's Guardian newspaper in which he claimed the British government's electronic eavesdropping agency GCHQ had gained secret access to fibre-optic cables carrying global Internet traffic and telephone calls, and was sharing the information with the NSA.

The charges against him include theft of government property, unauthorised communication of national defence information, and wilful communication of classified communications intelligence information to an unauthorised person.

Two of the charges were brought under the 1917 Espionage Act.