German police detained an alleged high-ranking Isis member in the southwestern town of Mutterstadt.
The German news agency dpa reported that the man, whose identity was not given, was detained after a tip from a prison inmate in the western city of Gelsenkirchen.
Dpa reported the information about the suspect came in connection with alleged threats against the German Bundesliga football league.
The suspect, who has not been named, was detained by Germany's special task force, SEC.
The state interior ministry of Rhineland Palatinate, where Mutterstadt is located, confirmed a terror arrest had been made but not say whether they were a member of Isis.
In a statement to German tabloid Bild, it said there were "indications something was planned" for the start of Bundesliga - which is the German equivalent of the English Premier League - but did not elaborate further.
The football season is due to begin again in Germany on 26 August and it not known which stadiums or teams were to be targeted.
The country is currently on high alert following a series of attacks over the past month.
In July, a failed asylum seeker blew himself up outside a bar in Ansbach in Bavaria after failing to get into a music concert.
A few weeks later, a German teenager of Iranian descent shot and killed nine people at a McDonalds in Munich.
Ali David Sonboly was described as "depressed" and "obsessed with mass shootings" and police do not believe he had any connection to Islamic extremism.
Additional reporting by AP
