German authorities have arrested an 18-year-old Iraqi man on suspicion of being an ISIS member. Federal prosecutors said Aqram A., whose full name was withheld on privacy grounds, was preliminary detained Wednesday in the southwestern Rhine-Neckar district. Prosecutors said that the man is suspected of joining ISIS in 2014 in the Iraqi city of Mosul where he completed military training for approximately four weeks. During the ensuing period, he worked as a guard and prepared fighting positions for the extremist group. In the summer of 2015, the suspect took part in fighting near the Iraqi town Beiji. He allegedly left Iraq in late 2015 and entered Germany in February 2016. Four Iraqis were arrested in Germany on similar charges last week. German police have been on high alert over potential militant attacks, particularly since December 2016 when a man hijacked a truck and ploughed into shoppers at a Christmas market in Berlin, killing 12 people. The attacker was shot dead by police in Milan four days later, and the rampage was claimed by ISIS. The terrorist group claimed responsibility for a number of other attacks in 2016.