An intense manhunt is underway in Germany and across much of Europe for the chief suspect in Monday's deadly truck attack on a Christmas market in Berlin.
Twelve people were killed and dozens were injured when a driver plowed a truck into a crowd of shoppers getting ready for the holiday.
A German arrest warrant named the suspect as Anis Amri, 24, from Ghaza, Tunisia; he is about 1.78 meters (5 feet 10 inches) tall, of average weight, and has black hair and brown eyes.
Media reports late Wednesday said police had raided two apartments in Berlin's Kreuzberg district in their hunt for Amri but came away empty-handed.
German Interior Minister Thomas de Maiziere would not confirm or deny media reports that Amri had been in touch with Islamic extremists. The Islamic State group has already claimed responsibility for the truck attack, which was similar to an assault carried out five months ago in Nice, France, that killed 86 people.
Prosecutors offered a reward of over $100,000 for information leading to Amri's capture. A wanted notice said, "Beware: He could be violent and armed!"
Police found Amri's identity papers in the wrecked truck; they named him as their chief suspect after learning that he had applied unsuccessfully for refugee status in Germany last year, and that he was facing deportation to Tunisia.
Prosecutors said Amri had used several aliases since coming to Germany in 2013. Stephan Mayer, a lawmaker from the governing conservatives, said authorities had been keeping an eye on Amri for some time.
In Tunisia, Amri's father said his son had left home for Europe seven years ago, and that he had spent time in detention in Italy before making his way to Germany.
Even before Amri was announced at the chief suspect, German Chancellor Angela Merkel had said it would be especially distressing if the killer was a refugee or asylum seeker looking for protection in Germany.
The truck, which was loaded with steel girders when it crashed through market stalls and mowed down shoppers on Monday, was stolen. Its Polish driver was found shot to death in the vehicle's cab.
Before Amri emerged as the main suspect, police had detained a Pakistani man on suspicion of involvement in the attack, but he was later cleared and released.
The market where this week's bloodbath took place, at the foot of the historic Kaiser Wilhelm Memorial Church in central Berlin, remained closed Wednesday, but more than 60 other Christmas markets across Berlin were open, with tightened security precautions in effect.
Security has also been boosted elsewhere in Germany, and in other European cities preparing for the Christmas and New Year holidays.