German police launched a manhunt Wednesday for a Tunisian suspected of driving the truck that ploughed through a Berlin Christmas market in a deadly assault claimed by the Islamic State jihadist group.
Media reports said asylum office papers believed to belong to the man were found in the cab of the 40-tonne lorry used in the attack that killed 12 people.
He applied for asylum in Germany in April and received a temporary residence permit, according to the daily Sueddeutsche Zeitung.
A previous suspect -- a 23-year-old Pakistani asylum seeker -- was released late Tuesday for lack of evidence, prompting fears of a killer on the loose and further rattling nerves in a shocked country.
Twelve people were killed when the Polish-registered articulated truck, laden with steel beams, slammed into the crowded holiday market late Monday, smashing wooden stalls and crushing victims.
The scenes revived nightmarish memories of the July 14 truck assault in the French Riviera city of Nice, where 86 people were killed by a Tunisian Islamist.
Twenty-four people remained in hospital, 14 of whom were seriously injured, Interior Minister Thomas de Maiziere said.
De Maiziere said several lines of inquiry were being pursued, but "we should let the security services do their job".
"No one will rest until the perpetrator or perpetrators have been caught," he told ARD public television.
The IS-linked Amaq news agency said "a soldier of the Islamic State" carried out the Berlin carnage "in response to appeals to target citizens of coalition countries".
There was no evidence to back the claim, nor was the perpetrator identified.
Germany is part of a US-led coalition fighting IS in Iraq and Syria.
Tunisia is one of the biggest suppliers of jihadist fighters, with some 5,500 of its nationals believed to be involved in combat in Syria, Iraq and Libya.
The attack comes at a delicate time for Chancellor Angela Merkel who is running for a fourth term in 2017 but has faced strong criticism over her decision last year to open the country's borders to refugees.
'New suspect very soon'
In a blow to investigators, federal prosecutors announced Tuesday they had to release the only suspect in custody after finding no forensic evidence to link him to Germany's deadliest attack in recent years.
The Pakistani man was detained late Monday after he was reportedly seen jumping out of the truck and fleeing the scene.
But officials had expressed growing doubts over whether they had the right suspect, and he denied the charges under repeated questioning.
Following the suspect's release, Berlin's police chief Klaus Kandt told ARD television "one or more" perpetrators were believed to be on the run and possibly armed.
Police said they were chasing up more than 500 tips from the public and examining DNA traces found in the cab of the truck.
"I am fairly confident that we will have a new suspect tomorrow or very soon," the head of the BDK police union, Andre Schulz, told public broadcaster ZDF late Tuesday.
Police were reportedly focusing their search for the Tunisian suspect in the western state of North Rhine-Westphalia.
Germany in mourning
A Polish man, killed with a gunshot, was found in the truck's passenger seat. The 37-year-old Pole named Lukasz worked for his cousin Ariel Zurawski's transport company in northern Poland.
Zurawski described him as a "good guy" and said his body showed signs of a struggle with the assailant or assailants.
"One person would not have been able to overpower him," Zurawski said of the relative he had grown up with, a heavyset man who weighed in at 120 kilos (265 pounds) and stood 183 centimetres (six feet) tall.
"We could see injuries. His face was bloodied and swollen," he told private news channel TVN 24, referring to a photo he received from Polish police.
An autopsy indicated that the driver was still alive at the time of the attack, the daily Bild reported.
Merkel visited the scene of the carnage for a minute's silence on Tuesday and then joined a service in the adjacent Kaiser Wilhelm Memorial Church.
Mourners placed flowers and candles at the site while German flags flew at half-mast and Berlin's landmark Brandenburg Gate was lit in the national colours in honour of the victims.
Europe has been on high alert for most of 2016, with bloody jihadist attacks striking Paris since last year and Brussels.
In Germany, 15 people were injured in two attacks in July in the southern state of Bavaria committed by asylum seekers and claimed by the Islamic State group.
Opponents were quick to seize on the carnage as proof that Merkel's liberal asylum policy had endangered the country.
Marcus Pretzell of the anti-immigration Alternative for Germany party labelled the Christmas market victims "Merkel's dead".