The authorities dismissed calls for him to be arrested on the same grounds as the former Chilean dictator Augusto Pinochet was held in Britain.
Izzat Ibrahim Al Douri was in Vienna for more than a week for medical treatment at the private Doeblinger clinic.
He was there on a month's visa issued by the Austrian authorities, but left early after human rights campaigners called for his arrest under the United Nations conventions against genocide and torture, to which Austria is a signatory.
These compel all countries to hold those suspected of being responsible for genocide or torture and formed the legal grounds on which Pinochet was arrested in Britain.
Vienna City Green Party MP Peter Pilz said he gave the Justice Ministry enough evidence to hold Al Douri who is said to be responsible for genocide and torture.
His accusations are backed by a number of pressure groups, including the New York-based Human Rights Watch which also called for Al Douri to be arrested.
Mr Pilz said yesterday, "I am ashamed of the Austrian government. The country is becoming a paradise for mass murderers. The government is good friends with the Iraqi regime. We have a foreign minister [Wolfgang Schuessel] who is helping these people to escape and an interior minister [Karl Schloegl] who gives these people Austrian holidays on `humanitarian grounds'. I cannot take them seriously any more. They have shown no respect for international law or for the victims. I am really very angry about this."
Al Douri was the commander in charge of the Northern Bureau Command of Iraqi forces which was responsible for the poison-gas attack against Kurds in Halabja in March 1988.
Up to 5,000 people were killed when Iraqi planes carpet-bombed the city and then smothered it with poison gas. Many who were not killed immediately collapsed and died later, on the run from further attack by the Iraqi military.
Al Douri was reported in the Washington Post in January 1991 as warning the people in another largely Kurdish north Iraq city that, "If you have forgotten Halabja, I would like to remind you that we are ready to repeat the operation". Reed Brody, advocacy director for Human Rights Watch, who was involved in the UK Pinochet case, said: "This is a slap in the face to the principle that Europe is an area of justice. It's very disappointing. Austria is clearly putting expediency above principle and politics above justice."
Al Douri was due to leave Vienna International Airport yesterday afternoon on a Royal Jordanian Airlines flight to Amman, from where he was expected to travel to Baghdad by road.
State Prosecutor Erich Wetzer said: "As far as I know he has now left the country. We are checking the information given to us by Peter Pilz, but there is quite a lot to be gone through. There was no urgency to arrest the man so we did not do so."
Asked what the point was of checking the evidence against Al Douri when he had already left the country, Dr Wetzer said: "It makes sense to continue working on it. He might want to come back."Reuse content