The brother of a Tunisian man suspected of driving a truck into a Christmas market in Berlin has urged him to surrender as authorities across Europe scrambled to track the suspect down.

Nearly three days after the deadly attack, which killed 12 people and injured 48 others, large bollards to stop trucks were being put in place at the scene.

Anis Amri's fingerprints were found in the cab of the truck, indicating that he was driving the vehicle, German officials said.

Sorry, this video has expired Anis Amri's fingerprints and identity papers were found in the truck used in the attack.

German authorities have issued a wanted notice for Mr Amri and offered a reward of up to 100,000 euros ($144,634) for information leading to the 24-year-old's arrest, warning that he could be "violent and armed".

"We can tell you today that there are additional indications that this suspect is with high probability really the perpetrator," Interior Minister Thomas de Maiziere said after visiting the Federal Criminal Police Office along with Chancellor Angela Merkel.

"Fingerprints were found in the cab, and there are other, additional indications that suggest this," he told reporters. "It is all the more important that the search is successful as soon as possible."

Frauke Koehler, a spokeswoman for federal prosecutors, specified that Mr Amri's fingerprints were found on the driver's door and the side of the vehicle.

"We believe that Anis Amri was steering the truck," she said.

Investigators searched properties in the western state of North Rhine-Westphalia and Berlin where Mr Amri is believed to have spent time, and also checked a bus in the southwestern city of Heilbronn after receiving a tip, Ms Koehler said. They did not make any arrests.

Family members of Mr Amri, speaking from his hometown of Oueslatia in central Tunisia, were shaken to learn that he was a suspect.

One of Mr Amri's brothers urged him to turn himself in.

"I ask him to turn himself in to the police. If it is proved that he is involved, we dissociate ourselves from it," brother Abdelkader Amri said.

He said Mr Amri, who turned 24 on Thursday, may have been radicalised in prison in Italy, where he went after leaving Tunisia in the wake of the Arab Spring uprisings.

Amri wasn't radicalised: mother

Italy's justice ministry confirmed media reports Mr Amri was repeatedly transferred among Sicilian prisons for bad conduct.

Prison records said he bullied inmates and tried to spark insurrections.

He served three years for setting a fire at a refugee centre and making threats, among other things, but Italy apparently detected no signs that he was becoming radicalised.

Mr Amri's mother insisted he had shown no signs of radicalisation and questioned whether he was really the market attacker.

Speaking from the Tunisian town of Oueslatia, Nour El Houda Hassani said poverty drove Mr Amri to steal and to travel illegally to Europe.

"I want the truth to be revealed about my son," she said.

"If he is the perpetrator of the attack, let him assume his responsibilities and I'll renounce him before God. If he didn't do anything, I want my son's rights to be restored."

An Israeli woman, Dalia Elyakim, has been identified as one of the 12 killed when a truck ploughed into the market in central Berlin on Monday evening (local time), Israeli Foreign Ministry spokesman Emmanuel Nahshon said.

The market in the centre of the capital was due to reopen today.

Large bollards to stop trucks are put in at scene of Berlin attack. ( ABC News: James Glenday )

German officials had deemed Mr Amri, who arrived in the country last year, a potential threat long before the attack and even kept him under covert surveillance for six months this year before halting the operation.

They had been trying to deport him after his asylum application was rejected in July but were unable to do so because he lacked valid identity papers and Tunisia initially denied that he was a citizen.

Documents belonging to Mr Amri, who according to authorities has used at least six different names and three different nationalities, were found in the cab of the truck.

Mr Amri left Tunisia years ago for Europe but had been in regular contact with his brothers via Facebook and phone.

AP/ABC