The head of Germany's domestic intelligence agency says authorities received a first tip in early September that the Islamic State group planned attacks on stations or airports in the country, and last week tracked down the bomb plot suspect who was arrested Monday.

Jaber Albakr, a 22-year-old Syrian who came to Germany as an asylum seeker, was overpowered and tied up in Leipzig by three compatriots, who alerted police. Officers on Saturday found explosives at an apartment in nearby Chemnitz, but Albakr evaded them.

Investigators believe Albakr was considering Berlin's airports as potential targets. Hans-Georg Maassen, the head of the domestic intelligence agency, told ZDF television Tuesday it received information at the beginning of September that IS was planning "attacks on infrastructure, stations and airports, in western Europe, particularly Germany."