Croatia\'s former prime minister Ivo Sanader was behind bars in a Zagreb prison Tuesday after being extradited from Austria as corruption probes involving him threaten to further damage the ruling HDZ party. The 58-year-old Sanader, who led the government from 2003 until 2009, was detained in Austria in early December on a Croatian warrant. He fled there just hours after his parliamentary immunity was officially lifted, enabling an in-depth probe of allegations that he was involved in a string of multi-million-euro (dollar) corruption affairs. Sanader, who has not yet been charged, will remain in custody for a month and is due to be questioned by anti-graft prosecutors on Thursday, his lawyer said. Political analysts emphasize that the political impact of Sanader\'s case should not be underestimated. The major corruption affairs that will be brought to light in the country facing economic hardship and gearing up for general elections later this year could harm the ruling HDZ, already lagging in the polls. Croatia\'s economy has been in recession since early 2009 and the recovery is expected to be slow. \"The HDZ has already paid a high political price for Sanader\'s rule as its rating was seriously damaged due to corruption\", political analyst Davor Gjenero told AFP. Sanader is notably alleged to have instructed state-run firms to make million-euro business deals with a local promotion agency. The money paid for the fictitious services ended up in the pockets of private individuals, including Sanader\'s own, and the coffers of his Croatian Democratic Union (HDZ) party, according to prosecutors. The national anti-graft bureau is also probing Sanader for allegedly taking bribes from Hungarian energy giant MOL. The HDZ is trying to cast Sanader as a lone agent but earlier this month a former party chief accountant was arrested, suspected of handing out illegally obtained cash to various party officials on Sanader\'s orders. \"After her arrest the Sanader case is no longer an issue of criminal and political responsibility of the former PM, but of political and criminal responsibility of the HDZ leadership,\" the Jutarnji List daily commented on Tuesday. Sanader\'s return comes as Croatia prepares for general elections, announced for December 4 by Prime Minister Jadranka Kosor. The Sanader affair could prove embarrassing for Kosor, his onetime close ally, as the party is trying to shift the blame for the corruption entirely on Sanader. If the former PM decides to hit back and expose who knew what, it could harm the HDZ\'s chances in the elections. The conservatives are already low in the ratings with the latest polls predicting a social democrat SDP win. Sanader suddenly stepped down in July 2009, in a move that shocked Croatia and heralded his transformation from a powerful leader to the \'Public Enemy Number One.\' \"Certainly for the next five months the Sanader case will be one of the most important judicial but also pre-electoral issues that will hang over HDZ\'s head like a sword,\" commented a Novi List columnist. \"But for Croatia\'s future it is even more important ... to determine if the model of ruling that enabled such corruption is irreversibly behind us or this is just a big show, offering up a scapegoat (Sanader) so that tomorrow ... it will be business as usual?\" The fight against corruption is among key criteria Zagreb has to meet to join the European Union. Croatia, set to join the bloc in mid-2013, has stepped up its anti-graft fight since Kosor took over.