Manhunt for Berlin suspect intensifies as anger grows

German authorities were under fire on Thursday after it emerged that the prime suspect in Berlin's deadly truck attack, a rejected Tunisian asylum seeker, was known as a potentially dangerous jihadist.

German prosecutors have issued a Europe-wide wanted notice for 24-year-old Anis Amri, offering a 100,000-euro ($1,04,000) reward for information leading to his arrest and warning he "could be violent and armed".

Asylum office papers believed to belong to Amri, alleged to have links to the radical Islamist scene, were found in the cab of the 40-tonne lorry that rammed through a crowded Christmas market in Berlin on Monday, killing 11.

The twelfth victim, the hijacked truck's Polish driver, was found shot in the cab.

Police on Wednesday searched a refugee centre in Emmerich, western Germany, where Amri stayed a few months ago, as well as two apartments in Berlin, the media reported.

But, as the Europe-wide manhunt intensified, questions were also raised about how the suspect had been able to avoid arrest and deportation despite being on the radar of several security agencies.

"The authorities had him in their crosshairs and he still managed to vanish," said Der Spiegel weekly on its website.

The Sueddeutsche Zeitung criticised police for wasting time focusing on a Pakistani suspect immediately after the truck assault, in what turned out to be a false lead.

"It took a while before the federal police turned to Amri as a suspect," it said.

The attack, Germany's deadliest in recent years, has been claimed by the Islamic State group.

Twenty-four people remain in hospital, 14 of whom were seriously injured.

Germany has boosted security measures following the carnage, beefing up the police presence at train stations, airports and at its borders with Poland and France.

In a revelation likely to stoke public anger, German officials said they had already been investigating Amri, suspecting he was planning an attack.

The interior minister of North Rhine-Westphalia state, Ralf Jaeger, said counter-terrorism officials had exchanged information about Amri, most recently in November, and a probe had been launched suspecting he was preparing "a serious act of violence against the state".

Berlin prosecutors said separately that Amri had been suspected of planning a burglary to raise cash to buy automatic weapons, "possibly to carry out an attack".

But, after keeping tabs on him from March until September this year they failed to find evidence of the plot, learning only that Amri was a small-time drug dealer, and the surveillance was stopped.