IS released a statement on Tuesday through its Amaq news agency that the attacker “in Berlin is a soldier of the Islamic State and carried out the attack in response to calls for targeting citizens of the Crusader coalition.”

Germany is not involved in anti-IS combat operations, but has Tornado jets and a refuelling plane stationed in Turkey in support of the coalition fighting militants in Syria, as well as a frigate protecting a French aircraft carrier in the Mediterranean.

The claim of responsibility came after German prosecutors released a man, from Pakistan who came to Germany last year, who was arrested on Monday night near the scene of the attack, suspected of driving the truck.

The man’s arrest was based on a description of a suspect who jumped out of the truck and fled but federal prosecutors say he denied any involvement and no forensic evidence linked him to the truck’s cabin.

Federal Criminal Police Office chief Holger Muench and other officials had expressed doubt earlier that the man in custody was driving the truck.

Muench also said police were yet to find a pistol which is believed to have been used to kill a Polish truck driver.

Berlin police are urging people to remain “particularly vigilant” and report “suspicious movements” to a special hotline.

Before Islamic State’s claim of responsibility, Germany’s top prosecutor, Peter Frank, told reporters the attack on the market outside the landmark Kaiser Wilhelm Memorial Church was reminiscent of July’s deadly truck attack in Nice.

Chancellor Angela Merkel insisted the attack cannot change Germans’ way of life.

“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 an emotional, nationally televised statement before heading to the scene of the attack in downtown Berlin. “A gruesome and ultimately incomprehensible act has robbed them of their lives.”

Later Merkel and German President Joachim Gauck attended a memorial service at the Kaiser Wilhelm Memorial Church and laid white roses outside the church.

Witnesses saw only one man flee from the truck after it rammed into the crowd at the Christmas market, smashing wooden stalls and travelling 60 to 80 metres before coming to a halt.

Six of those killed have been identified as Germans, and a man found shot and killed in the truck’s passenger seat was Polish. The other five people killed have not yet been identified. Twenty-five people remained hospitalised, 14 with serious injuries.

Merkel, who has been criticised for allowing in huge numbers of migrants last year, addressed head-on the possibility that an asylum-seeker was responsible for the carnage.

“I know that it would be particularly hard for us all to bear if it were confirmed that a person committed this act who asked for protection and asylum in Germany,” Merkel said. “This would be particularly sickening for the many, many Germans who work to help refugees every day and for the many people who really need our help and are making an effort to integrate in our country.”

Police have searched a large asylum seeker shelter at the city’s defunct Tempelhof airport with four men in their late 20s questioned but no one was arrested, the Associated Press has been told.

US President Barack Obama has expressed his condolences, while US President-elect Donald Trump said Islamic extremists must be “eradicated from the face of the Earth”.

– AP