A group of people gathered yesterday to sing 'We are the world' in front of the church in Berlin where a truck attack killed 12 people.
German police are looking for an asylum-seeker from Tunisia after finding an identity document under the driver's seat of the truck.
The federal prosecutor's office offered a reward of up to 100,000 euros 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 prosecutor's office said in a statement, in which it described Amri as 1.78 metres tall, with black hair and brown eyes.
German police commandos raided two apartments in the Berlin district of Kreuzberg late yesterday but did not find Amri, Die Welt newspaper reported, citing investigators.