"Russian law does not stipulate the duration of time for which a foreign citizen may stay in the airport's transit zone or liability for staying for a long time in an airport's transit zone without documents," the ministry said in a statement quoted by the Interfax news agency.

　　When a foreign citizen applies for a temporary stay on Russian territory, a territorial body of the Federal Migration Service (FMS) will make a decision on whether to grant a temporary asylum within three months, the statement said.

　　When granted asylum and passing a mandatory medical examination, the person "is entitled to receive a standard certificate from a territorial FMS body," it added.

　　Vladimir Volokh, head of the FMS' public council, said Friday that Snowden, who has been in Sheremetyevo airport's transit zone for more than a month, could be stuck there for another half a year until his legal status is cleared.

　　Volokh noted that as Snowden "has been hunted," remaining in the airport's transit area was preferable to transferring him to an FMS refugee shelter for security reasons.

　　On Thursday, US Ambassador to Moscow Michael McFaul said Washington had asked Russia not to "extradite" Snowden but to "hand him over" to the US authorities.

　　But President Vladimir Putin's spokesman Dmitry Peskov said Russia would not hand over Snowden to his home country.