Edward Snowden, the American man who revealed the extent of the US government's phone and internet surveillance, is seeking asylum in Ecuador.

Frustrating US efforts to extradite him, Snowden caught a commercial flight from Hong Kong to Moscow, apparently accompanied by at least one representative from the anti-secrecy group WikiLeaks.

Hong Kong said it allowed him to leave because of legal problems with the US extradition request.

Hours later, Ecuador confirmed it had received a request for asylum.

It is not clear how the former National Security Agency (NSA) contractor has been able to travel, given reports the US had revoked his passport since charging him with espionage and theft of government property.

The US justice department says it will seek cooperation from law enforcement authorities in any country where Snowden may travel.

Before announcing the asylum request on Twitter, Ecuador's foreign minister, Ricardo Patino, told journalists his country would study any petition

"Mr Snowden has informed us, which we were not aware of, that there's a large espionage system that the US has developed," he said.

"We have said that if Mr Snowden petitions our country for asylum, we will study it thoroughly, the way we did with Mr Assange and we are prepared to accept that petition then make a decision."

Ecuador has been sheltering WikiLeaks founder Julian Assange at its London embassy for the past year.

On its Twitter feed, WikiLeaks said Snowden "is bound for the Republic of Ecuador via a safe route for the purposes of asylum, and is being escorted by diplomats and legal advisers from WikiLeaks".

"Mr Snowden requested that WikiLeaks use its legal expertise and experience to secure his safety. Once Mr Snowden arrives in Ecuador his request will be formally processed," it added.

The WikiLeaks legal adviser accompanying Snowden is Baltasar Garzon, a former Spanish judge known around the world for ordering the arrest of former Chilean dictator Augusto Pinochet.

"The WikiLeaks legal team and I are interested in preserving Mr Snowden's rights and protecting him as a person," Mr Garzon said in a statement.

"What is being done to Mr Snowden and to Mr Julian Assange - for making or facilitating disclosures in the public interest - is an assault against the people."

Snowden flies to Moscow from Hong Kong

Snowden arrived Sunday in Moscow from Hong Kong, where he first fled with a trove of secrets taken from the NSA.

He was charged with espionage by the US authorities last week.

WikiLeaks gave no details about how it had helped to arrange the escape of one of the America's most wanted men.

Mr Assange, a 41-year-old former computer hacker from Australia, walked into the Ecuador embassy on June 19, 2012 and claimed asylum in a sensational bid to avoid extradition to Sweden for questioning over alleged sex crimes.

The South American country granted his request, accepting his fears that if sent to Sweden he might be passed on to the US and prosecuted for publishing thousands of classified war logs from Iraq and Afghanistan and a cache of diplomatic cables.

Britain has refused to grant him safe passage to Ecuador.