Snowden's Russian lawyer Anatoly Kucherena said the 30-year-old left the airport after receiving papers granting him temporary asylum for one year in Russia.

Snowden had been staying in the transit zone of Moscow's Sheremetyevo airport since his arrival there from Hong Kong on June 23.

He is wanted by the US government for leaking details of its intelligence programs. His revelations, including a phone data collection program and an internet monitoring program called PRISM, have caused a heated political debate around the world on the scope of US government spying.

Washington has revoked Snowden's passport and demanded his extradition.

A former US National Security Agency (NSA) contractor, Snowden had already been granted asylum by Bolivia, Nicaragua and Venezuela, but said he was afraid the US would monitor flights to these countries.

His revelations continue to have repercussions throughout the world. In Germany, there have been many questions asked of the country's political leaders after a report by news weekly Der Spiegel said documents provided by Snowden showed that German intelligence services cooperated closely with the NSA.

The report has put pressure on Chancellor Angela Merkel ahead of the September 22 national elections.

Snowden thanks Russia

In a statement released by the anti-secrecy group WikiLeaks, Snowden thanked Moscow but accused the United States of a lack of "respect" of international law.

"Over the past eight weeks we have seen the Obama administration show no respect for international or domestic law, but in the end the law is winning," Snowden said in the statement.

"I thank the Russian Federation for granting me asylum in accordance with its laws and international obligations."

WikiLeaks said Snowden left Sheremetyevo airport with the group's own legal adviser Sarah Harrison, who had been with him throughout his time there. It said the pair were headed to "a secure, confidential place."

United States 'disappointed'

The White House said on Thursday it was "extremely disappointed" with the decision, and that it could damage relations between the two countries.

Spokesman Jay Carney indicated it could force president Barack Obama to reconsider a decision to attend the G20 summit in St. Petersburg in September.

"Obviously this is not a positive development. We are evaluating the utility of a summit," Carney said, adding that the US was "extremely disappointed that the Russian government would take this step despite our requests in public and private."

"This move by the Russian government undermines a long-standing record of law enforcement cooperation, cooperation that has recently been on the upswing since the Boston Marathon bombings," Carney said.

tj, jr/hc (Reuters, AP, AFP)