The appeal arrived in Linz on Wednesday, said Barbara Feichtinger, spokeswoman for the prosecutor's office in Salzburg. The appeal will automatically prolong Sanader's stay in the extradition prison in Salzburg for one more month, Sanader's Austrian defence attorney Werner Suppan said.

Mr Sanader wants to be released from custody pending extradition proceedings, Suppan said, adding that the appeal was submitted on December 30.

Suppan said Sanader was not a flight risk and that there was no danger of his tampering with evidence.

He added that the court in Linz could make a ruling on the appeal in the next 14 days.

With his detention having been extended, there will be no detention hearing previously scheduled for January 27, the attorney said.

If the Linz Appellate Court decides to extend his extradition custody, the decision will lead to another extension of two months, a court official in Linz said.

Suppan said that Sanader's Croatian attorneys had still not studied the documents in his case, which was the reason why Sanader opposed a simplified extradition procedure.

Sanader has been in extradition custody in Austria since his arrest on December 10. He was arrested on a warrant issued by Croatian authorities which want him on suspicion of corruption.