Ansi Amri, the suspect in the Berlin Christmas market attack, was shot dead in Milan, Italy late Friday.
Amri was killed and one policeman injured during the shootout.
Chancellor Angela Merkel on Friday ordered a sweeping review of Germany’s security apparatus, which has drawn withering criticism after a known jihadist killed 12 people in a Berlin Christmas market.
The Scania-brand truck rammed up to 80 meters (260 feet) into the Christmas market near the iconic Kaiser Wilhelm Memorial Church, along the Kurfürstendamm shopping mile, at around 8:30 p.m. local time as locals and tourists gathered to enjoy the evening.
The arrests come as German authorities probe whether Amri had help before or after the attack.
Amri’s involvement in the attacks was initially missed by authorities, which some analysts believe would have been avoided if video cameras had been in use.
The fact that Amri was able to travel to Italy unhindered despite a Europe-wide arrest warrant has raised uncomfortable questions for intelligence agencies.
Amri served 3f years in jail in Italy for setting a fire at a refugee center and making threats, among other things – but authorities apparently detected no signs that he was becoming radicalized.
German police had monitored Amri since March but dropped the surveillance in September thinking he was primarily as a small-time drug dealer. A 12th victim, a Polish man identified as the truck’s legitimate driver, was discovered as a passenger in the destroyed cab with knife and gunshot wounds, German media reported.
A police spokesman said there was no connection between the Duisburg arrests and the Amri case.
There are widespread concerns that the December 19 terrorist attack on a Berlin Christmas market may set Germany on a more rightwing course.
But Interior Minister Thomas de Maiziere denied there had been a blanket security failure.
The 24-year-old had been at large since Monday’s attack, and European authorities had offered a reward of up to 100,000 euros (about $104,000) for information on his whereabouts.
“I told the Tunisian president that we have to significantly speed up the deportation process and increase the number of people sent back”.
Prior to the attack, Amri had repeatedly contacted “hate preachers”. However, the Islamic State gave no indication as to who the driver might have been or whether he was a direct operative or acting on his own due to sympathies he felt with the group.
A German security official said Wednesday that authorities had considered the man a possible terror threat previously and had been trying to deport him after his asylum application was rejected this summer.