Fugitive US leaker Edward Snowden will stay in the transit zone of the Moscow airport where he has been holed up for three weeks while Russian authorities process his asylum request, a lawyer helping him said Tuesday.

Anatoly Kucherena, a Russian lawyer who helped Snowden file an application for asylum in Russia earlier Tuesday, told AFP the former National Security Agency (NSA) contractor was happy with his treatment at the airport.

"While all procedural questions are being decided, he will remain in the transit zone of the airport," Kucherena told AFP in central Moscow when asked if Snowden would remain at Sheremetyevo airport until the asylum request was approved.

He confirmed that the asylum procedure could take up to three months although a shorter period is theoretically possible.

Kucherena said he met Snowden at the airport on Tuesday to file the asylum request, with a translator the only other person present.

"He is satisfied with how he is being treated by the employees of the airport," he added, declining to say how Snowden's security was being ensured at the airport.

Kucherena was among a group of rights activists, pro-Kremlin lawmakers and lawyers who met Snowden at the airport on Friday where he indicated that he wanted to file for asylum in Russia.

Snowden later called Kucherena asking for his help, the lawyer said.

"Right now he wants to stay in Russia. He has options. He has friends and a lot of supporters... I think everything will be ok," said Kucherena.

"If his request for asylum status is accepted, he has the same rights as you and me. There is no (other) way to resolve this situation."