According to the prosecutor the 22-year-old Syrian man worked as a security guard for Isis and fought with them in several places in Syria until January 2015.
After that he's believed to have travelled to Turkey and across the Mediterranean to Greece, where he joined other refugees along the Balkans route to Europe and claimed asylum in Salzburg.
On Monday the suspect told the judge that he had never joined Isis, and that during the time he is alleged to have fought with them he was working in a restaurant in Istanbul. He said that earlier he had fought with rebel forces against President Assad's government troops.
But prosecutors say that he boasted about having fought with Isis in a refugee centre in Salzburg. Police were able to gather evidence against him from his mobile phone, and from comments and photos of Isis atrocities that he posted on social media sites.
If found guilty, he faces up to ten years in prison. In a similar case, a 28-year-old Syrian man was sentenced to two years in prison.
Prosecutors are also due to press charges against a 26-year-old asylum seeker from Morocco, who investigators say planned terror attacks in Europe and probably had connections to the jihadists who carried out the November 13th Paris attacks which left 130 people dead.