BERLIN (AP) – German authorities say they have arrested a 25-year-old Syrian man on suspicion of being a member of the Islamic State extremist group.

Federal prosecutors say Faisal A.H., whose full name was withheld on privacy grounds, was detained Wednesday in the southwestern city of Tuebingen.

Prosecutors said Thursday the man is suspected of joining a militia in 2013 that fought against the Syrian government. Later that year the militia merged with the Islamic State group.

Prosecutors said A.H. was initially considered to be a government collaborator by IS, but after undergoing religious “re-education” and swearing allegiance to the group he was made to spy on people in the town of Tabqa and help clear homes seized by IS.

He allegedly left Syria for Germany at the end of 2014.