Tunisia's anti-terrorism police have raided the house of a wanted suspect in Berlin's deadly truck attack and questioned his family, Tunisian online newspaper al-Chorouk reports.
The family of the 24-year-old suspect, Anis Amri, has confirmed that his contact with them has not been regular since he left the country during the late 2010 uprising, the report adds.
A wanted notice for Anis Amri states that he is considered armed and dangerous, and offers a $150,000 reward for information leading to an arrest (IS). He was already under investigation by authorities for links to Islamic State.
He is currently the prime suspect in the Berlin attack, which killed 12 people and injured 48.
French police have been carrying out "preventive arrests" and checking on deployment of concrete barriers at Christmas markets amid fears of a secondary strike by Islamist militants.
Security sources in Berlin said German police were looking for the Tunisian man after finding an identity document under the driver's seat of the truck that ploughed into the Berlin market.
Annis Amri arrived in Germany last year but had his asylum request rejected. He was due for deportation.
He had failed to appear in court over an assault and forged documents, and was suspected of planning a serious act of violence against the state, according to North Rhine-Westphalia interior minister Ralf Jaeger.
Mr Jaeger also said the Tunisian national had been operating under several aliases, with at least six known names. He had also operated under Egyptian and Lebanese citizenship.
A government spokesman said organisers of Christmas markets had been contacted to verify all security measures, including baggage checks, following Monday's attack.
France's Interior Minister Bruno Le Roux said on Tuesday they were tracking dozens of people considered potentially dangerous. Many of them had been to Syria, where ISIS is based.