"There is a big worry that extremists in Germany, on the pretext of offering humanitarian help, could try to take advantage of the migrants' situation to convert and recruit those seeking asylum," said Hans-Georg Maassen, the president of the BfV domestic intelligence agency.
"Our attention is particularly focused on unaccompanied young refugees who could be easy prey for militants," Maassen said.
The remarks came just hours after police raided eight properties in Berlin, including a mosque association, that they suspect were being used by militants supporting fighting in Syria.
The comments will also feed into a divisive debate in Germany about how the country should deal with an influx of hundreds of thousands of migrants.
Maassen said that the number of ultra-conservative Salafist Muslims in Germany had risen to 7,900, compared with 7,500 in June. Some 740 militants from Germany, of which a fifth are women, have travelled to Syria and Iraq.
One third of those are now back in Germany, while 120 have died. Maassen said that there was no proof yet that militants had infiltrated the refugees.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ