BERLIN (Reuters) - German police are looking for an asylum-seeker from Tunisia after finding an identity document under the drivers seat of a truck that plowed into a Berlin Christmas market and killed 12 people, officials and security sources said on Wednesday.

The federal prosecutors office said it was offering a reward of up to 100,000 euros ($104,000) for information leading to the capture of the suspect, whom it identified as 24-year-old Anis Amri.

Beware: He could be violent and armed! the prosecutors office said in a statement, in which it described Amri as 1.78 meters (58) tall, with black hair and brown eyes.

Amris father and security sources told Tunisias Radio Mosaique that he had left Tunisia seven years ago as an illegal immigrant and had spent time in prison in Italy.

In Duesseldorf, Ralf Jaeger, interior minister of the western state of North Rhine-Westphalia (NRW), said the Tunisian appeared to have arrived in Germany in July 2015 and his asylum application had been rejected.

He seemed to have used different names and had been identified by security agencies as being in contact with an Islamist network. He had mainly lived in Berlin since February, but was recently in NRW, Jaeger added.

After being turned down for asylum, the man should have been deported but could not be returned to Tunisia because his documents were missing, he said.

Tunisia at first denied that this person was its citizen, said Jaeger, adding that German authorities started the process of getting new identity papers in August 2016. The papers werent issued for a long time. They arrived today.

The new details added to a growing list of questions about whether security authorities missed opportunities to prevent the attack, in which a 25-tonne truck mowed down a crowd of shoppers and smashed through wooden huts selling gifts, mulled wine and sausages. It was the deadliest attack on German soil since 1980.

Christmas markets have been a known potential target for Islamist militants since at least 2000, when authorities thwarted a plot to attack one in Strasbourg, France. And the modus operandi in Berlin was identical to that of a Bastille Day attack in the French city of Nice in July, when a Tunisian-born man rammed a lorry through a seaside crowd and killed 86 people.