German prosecutors say the man who was arrested after the Berlin lorry attack has been released because of insufficient evidence.
A Pakistani national only identified by the media was the only suspect held after Monday’s deadly lorry attack, which left 12 people dead and nearly 50 injured.
The man was captured in a park after reportedly fleeing the scene.
But federal prosecutors said on Tuesday night the man, who came to Germany last year as an asylum-seeker, denied involvement.
They noted that witnesses were able to follow the truck’s driver from the scene but lost track of him.
The man arrested matched witness descriptions of the truck driver - but investigators haven’t been able to prove that he was in the truck’s cab at the time of the attack.
Under German law, prosecutors have until the end of the calendar day following an arrest to seek a formal arrest warrant keeping a suspect in custody.
Later, the Islamic State extremist group claimed responsibility - its Amaq news agency saying in a statement that “the person who carried out the truck run over attack 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”.
German police are still hunting for the driver of the truck, which slammed into the downtown Christmas market Monday night.
Germany is not involved in anti-IS combat operations. But it does have Tornado jets and a refueling 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.
Police had urged members of the public to remain “particularly vigilant” as uncertainty loomed over whether they had arrested the correct suspect.
Germans have been urged to report any “suspicious movement” to a special hotline after the capital’s police chief said they were not able to confirm whether the man they arrested really was the driver of the vehicle.
Police said the truck was driven into the busy part of the German capital intentionally.
Berlin police chief Klaus Kandt said on Tuesday that it was not clear whether the man detained was really the driver.
“We haven’t been able to confirm it yet,” he told reporters earlier in the day.
The released suspect, who has denied involvement in the murders, is believed to have arrived in the country from Pakistan on December 31 last year and had applied for asylum, Germany’s top security official added.
Germany’s federal public prosecutor Peter Frank told a press conference that police were still unsure what the attacker’s motives may have been.
The Telegraph reports that Frank said it was unclear if the attacker had an Islamist background, adding: “For now we don’t know whether there was one attacker or several attackers. We also don’t know whether they had support.
“We have to think that the person who was arrested yesterday, a man of Pakistani nationality, we have to be open to the idea that he could possibly not have been the attacker.”
Frank added on Tuesday afternoon: “From the chosen target and behaviour of the perpetrator, you can infer an Islamist motive,” he said. “But we must continue to investigate in all directions.”
Speaking earlier today, German chancellor Angela Merkel said it would be “particularly sickening” if the Berlin market attacker is proven to be a refugee.
Merkel said the government “assumed” it was a terror attack, adding that: “We will find the strength to continue living life as we want to live it in Germany - in freedom, openness and together.”
The lorry struck the popular Christmas market outside the Kaiser Wilhelm Memorial Church late Monday as tourists and locals were enjoying a traditional pre-Christmas evening out near Berlin’s Zoo station.
“Our investigators are working on the assumption that the truck was intentionally driven into the crowd at the Christmas market on Breitscheidplatz,” Berlin police said on Twitter.
“All police measures concerning the suspected terror attack at Breitscheidplatz are being taken with great speed and the necessary care,” they said.
A man was arrested nearby. A passenger in the vehicle, believed to be a Polish national, was found dead in the lorry.
The Polish owner of the truck said he feared the vehicle may have been hijacked.
Ariel Zurawski said he last spoke with the driver, his cousin, around noon, and the driver told him he was in Berlin and scheduled to unload Tuesday morning. “They must have done something to my driver,” he told TVN24, the Associated Press reports.
Last night police urged people not to share videos from the scene on social media.
Police said the truck was registered in Poland, but that they were still investigating where it came from and who the driver is.
Television footage showed a large Scania truck with its windshield smashed out on the sidewalk alongside the market, with a swarm of ambulances nearby. A large Christmas tree with a gold star on top was toppled over nearby in the street.
Mike Fox, a tourist from Birmingham, UK, told HuffPost Germany at the scene in Berlin that the truck missed him by about three metres as it drove into the market, tearing through tables and wooden stands.
Fox said he helped people who appeared to have broken limbs, and that others were trapped under Christmas stands.
“It definitely looked deliberate,” Fox said. “My girlfriend said it appeared the truck was not stopping, there was no attempt to stop. It was careering, bashing into the stalls, and then carried on through.”
He added: “When it’s braking the cab dips down, when it’s not braking it carries on up. It didn’t look like it was stopping. There was no break sounds. It was clearly going straight on through.
“Whether it was driver drunk going on through, whether it was lost control or deliberate attempt, I can’t tell you. But there was no attempt to stop that we could see.”
The United States said the incident “appears to have been a terrorist attack”.
White House National Security Council spokesman Ned Price says the US condemns the attack “in the strongest terms.”
The White House said the US stands with Berlin in the fight against those who “target our way of life and threaten our societies”.
British Foreign Secretary Boris Johnson said: “My thoughts and condolences are withe the people of Germany following tonight’s terrible tragedy in Berlin, leaving so many dead and injured.”
Far-right groups and a nationalist party seized on Monday’s attack, blaming Merkel for what had happened.
“Under the cloak of helping people Merkel has completely surrendered our domestic security,” Frauke Petry, the co-chairwoman of the Alternative for Germany party wrote.
Manfred Weber, a member of Merkel’s conservative party and leader of the European Parliament’s biggest political grouping, cautioned against reaching sweeping verdicts following the attack. But he said it was important to ensure that extremists didn’t enter the country among those seeking refuge in Europe.
“The state must be able to check every refugee who comes here,” he told German public broadcaster ARD.