Snowden arrives at Moscow airport from Hong Kong

The BBC's Daniel Sandford says Edward Snowden is staying in a transit hotel before attempting to continue his journey

The US intelligence fugitive Edward Snowden has arrived in Moscow on a flight from Hong Kong.

But he is only thought to be in transit before leaving for Venezuela or Ecuador, via Cuba.

The US wanted him extradited from Hong Kong but the government said Washington had failed to meet its requirements.

Mr Snowden, an intelligence contractor, fled to Hong Kong in May after revealing extensive internet and phone surveillance by US intelligence.

The Aeroflot Airbus, flight SU213, landed at Moscow's Sheremetyevo Airport at 17:10 local time (13:10 GMT).

Russian media say he was picked up at the airport by either a Venezuelan or Ecuadorean embassy car.

Cars from the Ecuadorean embassy were seen outside the arrivals terminal

A source at the airline company was quoted as saying that he would fly on to Cuba, and from there to Venezuela. Both countries are believed unlikely to comply with any US extradition request.

It has been suggested he may travel on from Venezuela to Ecuador.

Wikileaks founder Julian Assange is currently sheltering in the Ecuadorean embassy in London after being granted asylum last year.

Wikileaks issued a statement saying that it has helped to find Mr Snowden "political asylum in a democratic country".

Mr Snowden's departure from Hong Kong casts further uncertainty over the prospect of him facing justice in the US.

On Saturday, the White House contacted Hong Kong to try to arrange his extradition. But the territory's administration, in a statement issued on Sunday, said the documents submitted by Washington did not "fully comply with the legal requirements under Hong Kong law".

As a result, Hong Kong says it requested further information from the US government.

However, the statement goes on: "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."

The US Justice Department has said it will seek cooperation from whichever country Mr Snowden arrives in.

"We will continue to discuss this matter with Hong Kong and pursue relevant law enforcement cooperation with other countries where Mr Snowden may be attempting to travel," Nanda Chitre, a spokeswoman for the justice department said in a statement.

University of Hong Kong law professor Simon Young expressed surprise at the Hong Kong authorities' decision on extradition.

He said that under local law, a very low threshold is required before a provisional warrant can be put in place.

"The US government will wonder why the Hong Kong government feels the surrender paperwork needs to be fully in place before the provisional warrant can be obtained," he said.

Senator Chuck Schumer told CNN it was "very disappointing what Hong Kong has done", while suggesting China had had an influence on their decision. He accused Russian President Vladimir Putin of "aiding and abetting" Mr Snowden's escape.

Mr Snowden left the US after leaking details of his work as an NSA (National Security Agency) analyst and the extensive US surveillance programme to Britain's Guardian newspaper and the Washington Post.

He has been charged in the US with theft of government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence.

Each of the charges carries a maximum 10-year prison sentence. The complaint is dated 14 June although it was made public only on Friday.

Meanwhile, NSA chief Keith Alexander told ABC News on Sunday there had been no warning that Mr Snowden had taken documents.

General Keith Alexander, speaking on ABC News' This Week: "He betrayed that confidence and stole some of our secrets"

"Clearly, the system did not work as it should have," he said,

Gen Alexander also said the spying agency was overhauling its operations to tighten security on contractors, including tracking the actions of system administrators like Mr Snowden.

"But at the end of the day we have to trust that our people are going to do the right thing," he said.

The leaks have led to revelations that the US is systematically seizing vast amounts of phone and web data under an NSA programme known as Prism.

Mr Snowden said earlier that he had decided to speak out after observing "a continuing litany of lies" from senior officials to Congress.

US officials have since defended the practice of gathering telephone and internet data from private users around the world.

They say Prism cannot be used to intentionally target any Americans or anyone in the US, and that it is supervised by judges.