So far no further information was available as to how and why he was freed.
In March 2013 Mahmoud was arrested in Turkey because of forged documents, with which he wanted to travel to Syria.
A spokesman from the Interior Ministry said he had no additional information and that it is currently unclear where Mahmoud is living.
Mahmoud released a video of him burning his Austrian passport after serving four years in an Austrian prison for joining and actively supporting al-Qaeda and its affiliates.
In April an extradition request from Austria was rejected by the Turkish authorities.
For years Mahmoud was one of the leaders of the Global Islamic Media Front, which translated into German videos and messages of al-Qaeda and its affiliated groups.
Mahmoud, originally from Egypt, was arrested in Austria in 2007 after authorities said they became alarmed when he started to buy ingredients for a possible suicide belt and the Media Front published a video threatening to carry out attacks in Germany and Austria if they did not withdraw their troops from Afghanistan.
He denied that he had anything to do with the production of the video or that he had any plans for a suicide attack.