Investigators found fingerprints of a Tunisian suspect in the Berlin Christmas market attack on the door of the truck that ploughed through the crowds, killing 12, German media said on Thursday.
A nationwide manhunt for the migrant was said to be underway.
Islamic State had claimed responsibility for the attack in which a truck smashed through wooden huts selling gifts, mulled wine and sausages on Monday evening.
It was the deadliest attack on German soil since 1980.
The media did not name their source for the report about 24-year-old Anis Amri’s fingerprints and police declined to comment.
The Berlin attack has raised concerns across Europe in the approach to Christmas, with markets in France, target of a series of militant attacks over the last year.
The development has led to tightening security with concrete barriers, as Troops were also being posted at churches.
The Berlin market reopened on Thursday ringed by concrete bollards.
Police in the western German city of Dortmund arrested four people who had been in contact with Amri, media reports said.
However, a spokesman for the chief federal prosecutor denied that and said he would give no further details on the operation.
Bild Newspaper cited an anti-terrorism investigator as saying it was clear in spring that Amri was looking for accomplices for an attack and was interested in weapons. (Reuters/NAN)
