Russia has granted fugitive US intelligence leaker Edward Snowden permission to leave the Moscow airport transit zone, airport sources have said.

Sources told Russia's RIA Novosti and Reuters news agency on Wednesday that a migration service document confirmed that his application for asylum was being considered, but it said it allowed Snowden to cross the Russian border so long as border guards did not  object.

The Interfax news agency said that Snowden could leave the airport, where he has been holed up for the past month, in the coming hours.

"The American is currently getting ready to leave. He is being provided with new clothes," Interfax said.

Anatoly Kucherena, Snowden's Russian lawyer who helped him to file his bid for temporary asylum in Russia on July 16, said that his client believed it would be unsafe to try to travel to Latin America soon because of the US efforts to return him to the United States to face espionage charges.

"He should get this certificate (allowing him to leave the airport) shortly," Kucherena said.

Kucherena said that Snowden's bid for temporary asylum in Russia might take up to three months to process, but he could pass through customs based on the initial response to his request.

RIA Novosti cited a source within the Russian border guards service as saying Snowden will be allowed to leave the airport as soon as he presents the document.

Snowden, whose presence at Moscow's Sheremetyevo airport since June 23 has strained the US-Russian relations, has not ruled out seeking Russian citizenship, Kucherena said.

Venezuela, Bolivia and Nicaragua have all have said they will grant him political asylum, but none is reachable by direct commercial flight from Moscow. 

Source: Agencies