Several witnesses at the Berlin Christmas Market were in shock as the truck went past them. (Reuters)
A "soldier" of the ISIS carried out a truck attack that killed 12 people at a Berlin Christmas market, a news agency linked to the jihadists said on Tuesday.
"A soldier of the ISIS carried out the Berlin operation in response to appeals to target citizens of coalition countries," the ISIS-linked Amaq news agency said in a statement posted online.
The statement did not identify the attacker.
The truck was rammed into shoppers at the Christmas market in Berlin on Monday night, killing 12 people and wounding dozens more in what German Chancellor Angela Merkel said was a likely "terrorist" attack.
Police arrested a Pakistani asylum-seeker soon after the attack but released him on Tuesday for lack of evidence, leaving investigators to pursue their hunt for the real perpetrator.
While Germany has so far been spared the devastating jihadist carnage that has hit neighbouring France and Belgium, it has suffered a spate of attacks this year.
In some cases, the assaults have been claimed by ISIS and carried out by asylum seekers.
On July 18, a 17-year-old asylum-seeker wielding an axe and a knife attacked passengers on a Bavarian train, injuring five people, before being shot dead by police.
The ISIS group released a video purportedly featuring the attacker announcing he would carry out an "operation" in Germany, and presenting himself as a "soldier of the caliphate".
A US-led military coalition that includes Germany has been carrying out air strikes against ISIS positions in Iraq and Syria since 2014.