German authorities had considered him a possible terror threat months before the attack, put him under covert surveillance for six months this year and tried to deport him after his asylum application was rejected this summer.
Authorities issued a notice to other European countries overnight seeking the arrest of 24-year-old Anis Amri, but initially held off on going public so as not to jeopardize the manhunt. After German media published photos of him and a partial name, federal prosecutors issued a public appeal for the information.
"A reward of up to 100,000 euros (USD 104,000) has been issued for information leading to the suspect's arrest."
A separate European arrest warrant from Germany obtained by The Associated Press states that Amri has at times used at least six different names and three different nationalities.
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He was described as being of average height and weight, with black hair and brown eyes.
Interior Minister Thomas de Maiziere cautioned that Amri's involvement in the attack wasn't yet certain even though documents in his name were found in the cab of the truck "This is a suspect, not necessarily the perpetrator," de Maiziere said after briefing Parliament's domestic affairs committee.
Twelve people were killed and 48 injured when a truck plowed into a popular Berlin market Monday evening in an attack claimed by the Islamic State group. Twelve of the wounded were still being treated Wednesday for very serious injuries and some were in critical condition, Berlin health officials said.
The suspect apparently arrived in Germany in July 2015 and has lived in three German regions since February, mostly in Berlin, said Ralf Jaeger, the interior minister of western North Rhine-Westphalia state.
"Security agencies exchanged information about this person in the joint counter-terrorism center, the last time in November," he said.
The tip warned that Amri might be planning a break-in to finance the purchase of automatic weapons for use in an attack. Surveillance showed that Amri was involved in drug dealing in a Berlin park and involved in a bar brawl, but found no evidence to substantiate the original warning.
The observation was called off in September, by which time Amri had disappeared from his regular haunts in Berlin, prosecutors said.
Separately, Amri's asylum application was rejected in July. German authorities prepared to deport him but weren't able to do so because he didn't have valid identity papers, Jaeger said. In August they started trying to get him a replacement passport.