German authorities are investigating 60 asylum seekers in the country on suspicion of belonging to or supporting terrorist organizations including Islamic State, the Federal Criminal Police Office BKA said Monday.
"Considering the ongoing migration movement into Germany, we have to assume that there are active or former members, supporters und sympathizers of terrorist organizations and Islamist war criminals among the refugees," the BKA said in a statement.
Of the 60 ongoing terrorist investigations, 20 have been launched in the past 10 weeks, the BKA said, adding that the organization had received a total of 410 tip-offs from local authorities in Germany's 16 federal states.
Three of the four violent attacks committed in Germany over the past week were perpetrated by migrants who came to the country as asylum seekers.
Late Sunday, a 27-year-old Syrian who had been denied asylum and was due for deportation to Bulgaria blew himself up outside a music festival venue in Ansbach, injuring 12 people.
On Monday, a 17-year-old asylum seeker registered as from Afghanistan attacked passengers of a Bavarian commuter train with an axe and a knife, injuring five people. The Islamic State group claimed responsibility.
On Sunday, a 21-year-old Syrian asylum seeker killed a woman and injured four others with a deli knife in Reutlingen in what investigators say was not an act of terrorism.
The BKA also said in its statement that the number of people who have left Germany to join the Islamic State in Syria has risen from 800 in May to 840.
Of the third that have since returned, about 70 people received combat training or took part in active fighting, the BKA said.