The Syrian national was plotting a chemical attack, and he was also recruiting people in order to commit a terrorist act, according to the German newspaper Bild.
Germany's Federal Intelligence Service received a tip from a foreign ally on the suspect and passed along the data to local authorities, who began tapping his phone, the newspaper added.
Berlin police reported that the 21-year-old Syrian was detained by special forces last week after getting involved in a brawl.
The Syrian has been placed in a detention facility.
No further details have been immediately available; an investigation is under way.