Austrian authorities have defended their decision not to extradite a wanted Nazi war criminal who was spotted supporting his national team at the European Football Championships.

Milivoj Asner, a Croatian citizen wanted for genocide, crimes against humanity and war crimes committed during World War Two in Croatia, is number four on the Simon Wiesenthal Centre list of most wanted surviving Nazi criminals.

Croatia has repeatedly demanded his extradition in order to put him on trial, but Austrian authorities have refused to hand him over, after court experts determined that he was suffering from Alzheimer Disease and old age dementia.

Mr Asner, 95, however, has been spotted in the company of his wife Edeltraut during a leisurely walk though the southern Austrian town of Klagenfurt, where the couple reside, and was filmed drinking wine and mingling with Croatian football fans.

However, officials at the Austrian Justice Ministry told The Times that they stood by their decision not to extradite Ms Asner, as he had been declared unfit to stand trial by medical experts on two separate occasions.

Thomas Geiblinger, the spokesman of the Justice Ministry, said: "According to Austrian law, no person who is unfit to stand trial or be questioned by authorities can be extradited. Two medical experts examined Mr Asner and determined that he was suffering from Alzheimer's and old age dementia, and that he would not be able to even be interrogated let alone stand trial."

But Efraim Zuroff, director of the Jerusalem-based Simon Wiesenthal centre, which aims to bring to justice Nazi war criminals, told The Times that Austria was a "safe haven for Nazi criminals" and that the revelations about Ms Asner showed that he was fit for trial and had to be extradited.

"Mr Asner is clearly in a good enough state to stand trial if he is able to sip wine, walk without assistance and support his national football team," he said.

"There simply in no political will in Vienna to tackle the issue of surviving Nazi criminals who have successfully avoided facing justice in the country for decades. I am about to send a letter to the Austrian Justice Minister and demand immediate action against Ms Asner."

According to Mr Zuroff, Mr Asner, who has now changed his name to Georg Aschner, was involved in the deportation of hundreds of Jews, Serbs and Roma during his time as a chief of police in the Croatian town of Pozega during the war. Croatia was then a close ally to Nazi Germany and ruled by the Ustasha, a fascist regime installed by the Nazis.

He is one of several prominent Nazi criminals who resided in Austria without ever been brought to justice due to what is perceived as lenience on behalf of Austrian authorities.

Dr Heinrich Gross, an Austrian psychiatrist accused of killing disabled children in the Nazi era, died of old age in 2005 in his home in Vienna. He continued his career as a doctor after the war, despite evidence of his crimes.

In addition, Erna Wallisch, a former concentration camp guard, died this February in Vienna aged 86 without having to stand trial despite testimonies of witnesses that she had been involved in murders of prisoners.

"There hasn’t been a trial of a Nazi criminal in Austria for over 30 years – but not for lack of Nazis, but rather because authorities are not willing to act," Mr Zuroff said.

Mr Zuroff also claims that his request to have an independent medical expert examine Mr Asner to determine whether he was fit to be extradited was rejected by Austrian authorities. The Austrian state has itself appointed the two experts who have so far examined Mr Asner.

Mr Asner gave an interview to The Sun this week, in which he appeared articulated and rejected the accusations against him. When confronted about the allegations of his involvement in war crimes and deportations, he said: "It is not true. It’s hilarious. I didn’t have anything to do with it. I was just an officer with the justice department – a lawyer. I never did anything bad against anybody."

Mr Zuroff claims the images and the statements of Mr Asner testify to his ability to stand trial and he is now demanding that the Austrian Justice Minister Maria Berger reopens his case and orders an immediate deportation.

But Mr Geibliner, the Austrian Justice Ministry spokesman, said: "Our hands are tied. If someone goes out in the open for a bit of sun, it still doesn’t mean that they are fit for trial. We are obliged to follow the recommendations of medical experts appointed by a court of law, and two experts have on two separate occasions reported that Mr Asner is suffering from severe dementia.

"The only thing to do would be to possibly order a new medical examination if the local prosecutors decide there are grounds for that."

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