Three people including the nephew of the Berlin Christmas market attacker Anis Amri have been arrested in Tunisia.
Tunisia's Interior Ministry said Amri - who was shot dead on Friday - had sent his 18-year-old nephew Fedi money to join him in Europe.
Twelve people were killed and dozens more injured in the attack on Monday.
Police in Germany have raided homes across the country as the hunt continues for the suspect of Monday's Christmas market attack in Berlin.
Three days after the attack, in which 12 people were killed and 48 hospitalised, the family of the main suspect, 24-year-old Anis Amri have made an emotional appeal for him to hand himself in.
Reporting from Berlin, Rohit Kachroo said: "There are claims in the US the Americans were so concerned about Mr Amri that they had previously put him on a US no-fly list.
"It is also claimed they are aware he researched explosives and that he communicated with IS in Syria using encrypted phone apps.
"But despite this wealth of information from networks, from family and friends, there is a growing desperation around this investigation - symbolised by the rare offer of the 100,000 Euro reward for extra information."
The funeral for the lorry driver killed in the Berlin Christmas market attack has taken place in his home country of Poland.
Footage has emerged of the final moment before a truck ploughed into a crowd of people at a Christmas market in Berlin.
A man is being hunted by German police after a lorry ploughed into a Berlin Christmas market on Monday, killing 12, but who is the suspect?