"What Austria has done is a very big mistake... This is the last thing a European country should do," Foreign Minister Abdullah Gul said.

"This erodes the foundations of the international struggle against terrorism," Gul said in televised remarks from the central city of Kayseri, where he is campaigning ahead of Sunday's general elections.

The man at the middle of the row is Ali Riza Altun, a founding member and the chief financial operator of the separatist Kurdistan Workers' Party (PKK), listed as a terrorist group by Turkey, the European Union and the United States.

Altun reportedly emerged in Austria in early July after fleeing France, where he was briefly detained in February.

"Police in Austria determined that he was holding a fake identity card, but still put him on a plane and sent him to Iraq," Gul said.

"This is incredible," the minister complained. "They know he is wanted on an Interpol warrant, that he is involved in illegal activities and, despite the fact that he is a Turkish citizen and should be extradited to Turkey, they send him to Iraq."

The Austrian ambassador to Turkey was summoned to the foreign ministry Wednesday and handed a "very strong protest," Gul said.

Turkey is now seeking Altun's extradition from Iraq, he said.

Ankara has long accused European countries of tolerating PKK activity and failing to close down organisations affiliated to the group.

It says the PKK obtains much of its finances through drug trafficking, people smuggling, extortion and money laundering in Europe, where it has an extensive network.

Austria's decision to send Altun to Iraq is particularly galling for Turkey at a time when tensions are running high between Ankara and Baghdad over the safe haven that the PKK enjoys in northern Iraq.

Ankara has threatened a cross-border operation to crack down on PKK bases in the region where, it says, the rebels obtain weapons and explosives for attacks inside Turkey.

Turkey last week demanded an official explanation from the United States on how US weapons ended up in PKK hands.

Officials suggest that the Iraqi Kurds, staunch US allies who control northern Iraq, are giving the PKK weapons they receive from the United States.