BERLIN — Germany's top domestic security official is warning that ISIS is actively recruiting among the new waves of refugees arriving in the country.

Hans-Georg Maaßen, president of Germany's Federal Office for the Protection of the Constitution, told Die Welt that Islamist terror groups are busy trying to recruit refugees, especially young men who have traveled without their families and are looking for people to connect with.

"We have counted about 300 direct approaches," Maaßen says. "And we do think that the real number is a lot higher than the reported cases we know of. We especially worry about the many unaccompanied minors. The recruitment process holds an enormous potential for radicalization."

Radical elements in mosques and Arabic-speaking criminal networks also see the potential in connecting with refugees, he said, "especially young and physically strong men."

Maaßen further warns that the ISIS terror group is using the flood of refugees to infiltrate combatants. "ISIS is planning on attacking Germany and German values," he told Die Welt. German cities have been named in the same context as Paris, London and Brussels.

André Schulz, head of the Federation of German Detective Officers (BDK), says that there are thousands of immigrants in Germany whose origins are unknown. "We don't know where they came from and where they are right now," Shulz says. He characterizes that situation as unacceptable for a constitutional state.

"The assumption of some politicians that it's highly unlikely that ISIS combatants would enter the country by mixing in with refugees is simply naïve," Shulz said.

German authorities are currently looking for dangerous Islamists who have disappeared — among them 76 violent individuals with outstanding arrest warrants. In 2015, approximately 150 Islamists left Germany to return to Iraq or Syria. Over the years, 800 departures have been counted. Among them, approximately 130 are dead, 80 of them killed in fighting last year. About 70 have actively participated in battles or have gone through some sort of a military training.

*This is an abbreviated version of the original article.