A plane believed to carry Edward Snowden, the former contractor for the U.S. National Security Agency, lands in Moscow's Sheremetyevo airport, June 23, 2013. [Photo/Agencies]

HONG KONG/MOSCOW - Fugitive former U.S. spy agency contractor Edward Snowden is seeking asylum in Ecuador, the Quito government said on Sunday, after Hong Kong let him leave for Russia despite Washington's efforts to extradite him on espionage charges.

In a major embarrassment for the Obama administration, an aircraft thought to have been carrying Snowden landed in Moscow, and the anti-secrecy group WikiLeaks said he was "bound for the Republic of Ecuador via a safe route for the purposes of asylum."

Ecuadorean Foreign Minister Ricardo Patino, visiting Vietnam, tweeted: "The Government of Ecuador has received an asylum request from Edward J. #Snowden."

Ecuador has been sheltering WikiLeaks' founder Julian Assange at its London embassy for the past year, and Ecuador's ambassador to Russia said he expected to meet Snowden in Moscow on Sunday.

Snowden, who worked for the U.S. National Security Agency in Hawaii, had been hiding in the former British colony, which returned to China in 1997, since leaking details about U.S. surveillance activities at home and abroad to news media.

U.S. authorities had said only on Saturday they were optimistic Hong Kong would cooperate over Snowden.

On Friday, U.S. authorities charged Snowden with theft of U.S. government property, unauthorised communication of national defense information and willful communication of classified communications intelligence to an unauthorised person, with the latter two charges falling under the U.S. Espionage Act.

Earlier on Sunday, a source at the Russian airline Aeroflot said Snowden would fly on from Moscow within 24 hours to Cuba, although that source said he planned to go on to Venezuela. The chief of Cuba's International Press Center, Gustavo Machin, said he had no such information though pro-government bloggers heaped praise on Snowden and condemned U.S. spying activity.

Ecuadorean Ambassador Patricio Alberto Chavez Zavala told reporters at a Moscow airport hotel that he would hold talks with Snowden and Sarah Harrison, a WikiLeaks representative.

In their statement announcing Snowden's departure, the Hong Kong authorities said they were seeking clarification from Washington about reports of U.S. spying on government computers in the territory.

The Obama administration has previously painted the United States as a victim of Chinese government computer hacking.  

At a summit earlier this month, Obama called on his Chinese counterpart Xi Jinping to acknowledge the threat posed by "cyber-enabled espionage" against the United States and to investigate the problem. Obama also met Putin in Northern Ireland last week.

A spokesman for the Hong Kong government said it had allowed the departure of Snowden - considered a whistleblower by his supporters and a criminal or even a traitor by his critics - as the U.S. request for his arrest did not comply with the law.

In Washington, a Justice Department official said it would seek cooperation with countries Snowden may try to go to and sources familiar with the issue said Washington had revoked Snowden's U.S. passport. State Department spokeswoman Jen Psaki said revoking the passport of someone under a felony arrest warrant was routine. "Such a revocation does not affect citizenship status," she said.

"It's a shocker," Simon Young, a law professor with Hong Kong University said of the case. "I thought he was going to stay and fight it out. The U.S. government will be irate."

The issue has been a major distraction for Obama, who has found his domestic and international policy agenda sidelined as he has scrambled to deflect accusations that U.S. surveillance practices violate privacy protections and civil rights. The president has maintained that the measures have been necessary to thwart attacks on the United States.

The White House had no immediate comment on Sunday's developments.

WikiLeaks said Snowden was accompanied by diplomats and that Harrison, a British legal researcher working for WikiLeaks, was "accompanying Mr Snowden in his passage to safety."    

"The WikiLeaks legal team and I are interested in preserving Mr Snowden's rights and protecting him as a person," former Spanish judge Baltasar Garzon, legal director of WikiLeaks and lawyer for Assange, 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."

A spokesman for Wikileaks refused to make any comment about possible routes to Ecuador. Asked why Ecuador, he replied "That is something that Mr. Snowden needs to reply to. ... It was a decision taken by him. ... Various governments were approached."

Iceland refused on Friday to say whether it would grant asylum to Snowden. Putin's spokesman, Dmitry Peskov, said this month that Russia would consider granting asylum if Snowden were to ask for it and pro-Kremlin lawmakers supported the idea, but there has been no indication he has done so.

Hong Kong's South China Morning Post newspaper earlier quoted Snowden offering new details about U.S. surveillance activities, including accusations of U.S. hacking of Chinese mobile phone firms and targeting of China's Tsinghua University.

Senator Dianne Feinstein, chair of the Senate Intelligence Committee, said Snowden needed to be caught and brought back for trial as secrets he was carrying could do a lot of damage to U.S. interests.

Documents previously 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.

The head of the National Security Agency, General Keith Alexander, said he did not know why it failed to prevent Snowden leaving Hawaii for Hong Kong with the secrets.

"It's clearly an individual who's betrayed the trust and confidence we had in him," he told the ABC News "This Week" program.

He said procedures had since been tightened.

"We are now putting in place actions that would give us the ability to track our system administrators, what they're doing, what they're taking, a two-man rule. We've changed the passwords. But at the end of the day, we have to trust that our people are going to do the right thing."