Polish-born film director Roman Polanski awaits a public talk in Potsdam in this February 19, 2009 file photo. Swiss authorities denied a request to release Polanski on bail after he was arrested in September after fleeing sentencing for having unlawful sex with a 13-year-old girl in 1977, a government spokesman said on Tuesday. REUTERS/Hannibal Hanschke

Swiss authorities on Tuesday rejected an appeal by lawyers for Roman Polanski, who was arrested in September after fleeing America in 1978 from an underage sex charge, to release the film director from prison.

Authorities also urged a Swiss court dealing with his extradition warrant to reject another appeal by Polanski's lawyers to have him freed and to refuse any request to release the 76-year-old Oscar winning film director on bail.

Polanski pleaded guilty to having sex with a 13-year-old girl in 1977 but fled the United States on the eve of his 1978 sentencing because he believed an American judge might overrule his plea and put him in jail for 50 years.

In our view, there is still a very high risk that he will flee and that a release on bail or other measures after a release cannot guarantee Polanski's presence in the extradition procedure, Federal Office of Justice spokesman Folco Galli said.

Polanski's lawyers had appealed to the Federal Office of Justice to reconsider his arrest on a U.S. extradition warrant.

They also lodged an appeal with the Swiss Federal Penal Court which can still decide to release Polanski on bail.

Swiss authorities have previously said it was very unlikely Polanski would be released on bail.

The justice office had asked the Swiss Penal Court to reject Polanski's appeal to be released, Galli said.

The director, who holds dual French and Polish citizenship, was arrested at the request of the United States when he flew into Switzerland on September 26 to receive a lifetime achievement prize at a film festival.

The filmmaker, who won the best director Oscar for 2002 Holocaust film The Pianist, was also accused of giving drugs and alcohol to the girl.

Polanski had reached a deal with Los Angeles prosecutors to plead guilty to the sex charge and receive 42 days in prison for psychiatric tests -- time he had already served. But Polanski believed the judge might overrule the plea and sentence him to as much as 50 years in jail.