Authorities arrested the man "on suspicion of spreading al Qaeda propaganda online and for procuring materials which could be used to make a bomb," prosecutors said Friday in a written statement.
Searches of a flat in Offenbach, Germany, and a business in Frankfurt, Germany, turned up a small amount of an "explosive substance" and a home-made electronic device.
An initial assessment suggests that the items "could be used to ignite explosives," prosecutors said.
The man holds dual German-Turkish citizenship, they said. The statement from prosecutors identified him only as Adnan V.
Al Qaeda and the Taliban released threatening videos before Germany's recent national elections, but prosecutors said Friday that "there appears to be as yet no direct link" between those videos and the German-Turkish man.