Islamic State extremists claimed responsibility Tuesday for the truck attack in Berlin that killed at least 12 people and wounded dozens more at a crowded Christmas market in the German capital.
The claim was posted late Tuesday on the website of the group's Amaq news agency. It said the attack was carried out "in response to a call for targeting citizens of the Crusader coalition."
The statement came a short while after German police released a lone suspect captured Monday evening after a huge truck smashed into an open-air market where locals and tourists were partaking in traditional Christmas festivities.
A firefighter walks in front of a truck at the site of an accident at a Christmas market on Breitscheidplatz square near the fashionable Kurfuerstendamm avenue in the west of Berlin, Germany, Dec. 19, 2016.
The Chief Federal Prosecutor's Office says it released the suspect, a Pakistani national, because investigators did not have enough evidence to charge him with a crime.
"The investigation up to now did not yield any urgent suspicion against the accused," the prosecutor's statement read.
German Chancellor Angela Merkel, who laid white roses at the attack site outside the landmark Kaiser Wilhelm Memorial Church on Tuesday, said she was "shocked, shaken and deeply saddened by the attack.
The Kaiser Wilhelm Memorial Church Christmas Market in Berlin
"Twelve people who were still among us yesterday, who were looking forward to Christmas, who had plans for the holidays, aren't among us anymore," she said in a nationally televised statement. "A gruesome and ultimately incomprehensible act has robbed them of their lives."
Earlier Tuesday, the head of Germany's Federal Criminal Police force said police have not yet found the gun believed to have been used to kill the truck's driver before it was stolen.
German Chancellor Angela Merkel signs the condolence book at the Memorial Church in Berlin, Germany, Dec. 20, 2016, one day after a truck ran into a crowded Christmas market in Berlin and killed several people.
Berlin Senator for the Interior Andreas Geisel announced new security measures to be implemented around the nation’s capital in response to the attack and asked organizers of other Christmas markets to shut down for the day to honor the victims.
Witnesses said the popular Christmas market was packed with tourists and locals when the truck, believed to have been traveling in excess of 60 kilometers an hour, slammed into it. Authorities said the vehicle was loaded with steel beams.
The White House offered condolences in a statement that condemned the attack.
The U.S. State Department had earlier called for caution in market places and other public sites across Europe. A published U.S. travel alert said extremist groups were focusing their attention "on the upcoming holiday season and associated events." It also warned U.S. citizens on the continent to be on the alert for "self-radicalized" extremists, who it said could strike without warning.
The Polish owner of the truck, which had Polish license plates, said the vehicle driven by a relative was most likely hijacked after German authorities had him identify the body of his dead employee.
"His face was swollen and bloodied. It was really clear that he was fighting for his life," Ariel Zurawski told German broadcaster TVN.
Monday's crash bore strong similarities to a truck attack earlier this year in southern France that killed scores of people as France celebrated a national holiday.
French police linked that July 14 attack, which killed 86 people and wounded more than 400 others, to a Tunisian national with reputed links to Islamic State extremists.