German police are searching for a Tunisian man over Monday’s Berlin Christmas market attack, reports say.
According to a temporary-stay permit found in the cab of the lorry that ploughed into crowds, “Anis A” was born in 1992 in the city of Tataouine.
Searches are said to be under way in the North Rhine-Westphalia region.
The suspect may have been injured in a struggle with the Polish driver, found murdered in the cab. A further 11 people were killed by the lorry.
Chancellor Angela Merkel has met her security cabinet to discuss the investigation into the attack.
The Tunisian suspect is also known to use false names, security sources told German media and Reuters news agency.
His name was given using a German convention whereby suspects are identified by their first name and initial.
He is reported to have travelled to Italy in 2012 and then on to Germany in 2015 where he applied for asylum and was granted temporary leave to stay in April of this year.
He is said to be known to police and was briefly detained in August with fake Italian identity documents.
Sueddeutsche Zeitung reports that the suspect moved within the circle of an Islamist preacher, Ahmad Abdelazziz A, known as Abu Walaa, who was arrested in November.
Broadcaster N-TV said measures were “now imminent” in North Rhine-Westphalia but there were no further details.
Officials have not confirmed the reports so far.
‘Struggle with driver’
Some 49 people were also injured when the lorry was driven into crowds at the Breitscheidplatz Christmas market. So-called Islamic State said one of its militants carried out the attack but offered no evidence.
Polish citizen Lukasz Urban was found dead on the passenger seat with gunshot and stab wounds.
Investigators quoted by German media say there is evidence that, despite being stabbed, Mr Urban wrestled him for the steering wheel.
One official quoted by Bild newspaper said it appeared from the post-mortem examination that the driver had survived up to the attack and was shot dead when the truck came to a halt. No gun has been recovered.
Ariel Zurawski, the owner of the Polish transport company, said he had been asked to identify Mr Urban from photographs.
“His face was swollen and bloodied,” he told broadcaster TVN. “It was really clear that he was fighting for his life.”
Company manager Lukasz Wasik described Mr Urban as a “good, quiet and honest person” and said he believed he would have defended the lorry “to the end”.
Police say they are acting on hundreds of tips from the public and are examining DNA traces from the cab of the truck.
German Interior Minister Thomas de Maiziere said he was confident that the person responsible would be caught soon.
Speaking outside the Charite Hospital in Berlin, he said: “They should feel that they are not alone and that apart from the doctors here, people across the country are hoping and waiting for them to recover.”
Officials released the only detained suspect on Tuesday, saying there was no evidence to link him to the attack.
The man, a Pakistani national named as Naved B, was detained about 1km (0.6 miles) from the market but strongly denied any involvement.
Police said there were no forensic clues to link him to the vehicle, and had expressed doubt about his involvement soon after his arrest.
The IS group claimed the attack through its self-styled news agency, saying it was “in response to calls to target nationals of the coalition countries”.
Prosecutor Peter Frank told reporters that the style of attack and the choice of target suggested Islamic extremism.
But Mr de Maiziere reacted cautiously to the claim, saying “several lines of investigation” were being pursued.
Monday’s incident mirrored the lorry attack on Bastille Day crowds in the French city of Nice on 14 July, which was also claimed by IS.
Both IS and al-Qaeda have urged their followers to use vehicles as a means to attack crowds.