Former US spy agency contractor Edward Snowden applied for temporary asylum in Russia on Tuesday after three weeks holed up at a Moscow airport trying to avoid prosecution in the United States on espionage charges.

Snowden is seeking refuge in Latin America after leaking details of US government surveillance programmes, but has not risked taking any flight that might be intercepted by the United States since flying in from Hong Kong on June 23.

"He reached the conclusion that he needs to write an application for temporary asylum (in Russia), and this procedure has just been done," Anatoly Kucherena, a lawyer who met Snowden on Friday along with human rights activists, told Reuters.

"For now he is not going to go anywhere. For now he plans to stay in Russia," he said, adding that if Snowden were granted temporary asylum, he should have the same rights as other citizens and be free to work and travel in Russia.

The asylum application could end his time in limbo but risks deepening tension between the US and Russia, which has refused to expel him to his homeland for prosecution.

The head of Russia's Federal Migration Service (FMS) confirmed the agency had received Snowden's application. Anti-secrecy group Wikileaks, which has been helping Snowden, said on Twitter that he had applied for "a temporary protection visa".

Snowden, 30, is trapped in the transit zone of Moscow's Sheremetyevo airport, an area between the runway and passport control which Russia regards as neutral territory.

He said on Friday he would seek refuge in Russia only until he can travel to one of the three Latin American countries ready to give him political asylum - Bolivia, Venezuela and Nicaragua.

He said the United States and its allies were preventing him from reaching those countries. Washington has revoked Snowden's passport and urged other nations not to help him reach an asylum destination.

Kucherena said he expected a decision on Snowden's asylum request "soon", though the Federal Migration Service has up to three months to decide on the application.

PUTIN'S CONDITIONS

The process for seeking temporary asylum is different from that for political asylum, which Kucherena said would require a decree from President Vladimir Putin.

Putin has rejected repeated US calls to send Snowden to the United States, but has said he does not want the fugitive to harm already strained relations with Washington.

Snowden is useful as a propaganda tool for Putin, who accuses the US government of preaching to the world about rights and freedoms it does not uphold at home.

But Putin has invited President Barack Obama for a summit in Moscow in September and both countries have signalled they want to improve ties.

Putin has said twice that Snowden must stop all activities "aimed at harming our American partners" if he wants political asylum in Russia, but he has not made clear whether the condition applies to temporary asylum as well.

Temporary asylum is granted by the FMS, but Putin would be expected to make the final decision himself, even though he has tried to distance himself from Snowden's predicament.

Putin said on Monday he hoped Snowden would leave as soon as he could, but left the door open for granting him asylum, saying there were signs the American fugitive was moving towards meeting the conditions he has set.

Temporary asylum can be granted for up to a year, with the possibility of extension. - Reuters