The Berlin Christmas market where 12 people were killed on Monday by a suspected Islamist extremist who drove a truck into a crowd has reopened.

Police have installed concrete barriers to prevent a repeat attack.

Locations in Dortmund, Emmerich and Berlin were raided overnight in the hunt for Tunisian suspect Anis Amri.

Amri is the subject of a Europe-wide arrest warrant. His ID was left in the lorry and now his fingerprints have been found on the door, reports say.

The lights were dimmed and the mood was sombre as the Breitscheidplatz market reopened.

Candles and flowers were laid for those who died - they included at least six Germans, an Israeli tourist and an Italian woman - and for the 49 people who were injured.

Apartments were raided in Berlin and the western city of Dortmund and around 80 officers searched a refugee centre in Emmerich - all reportedly sites linked to Anis Amri.

Prosecutors denied reports by Bild newspaper that four people who were in contact with Amri had been arrested.

Amri's name came to the attention of German counter-terror services last month and he reportedly moved in the circle of extremist preacher Ahmad Abdelazziz A, known as Abu Walaa, who was arrested last month and charged with supporting so-called Islamic State (IS).

The Ruhrnachrichten news website said Amri had lived in Dortmund from time to time and residents at one block of flats said he had spent time with a German of Serbian origin, Boban S, who was arrested last month along with Abu Walaa.

Amri was on a US no-fly list, had researched explosives online and had communicated with IS at least once via the Telegram Messenger service, the New York Times reported.

IS has said one of its militants carried out the attack but has offered no evidence.

Amri had offered himself for a suicide attack, Spiegel magazine reported, quoting communications intercepted for the prosecution of hate preachers in Germany.

However, what he said was not believed to be explicit enough for him to be arrested, the magazine said.

Amri had also been put under surveillance in Germany earlier in the year on suspicion of planning a robbery to pay for automatic weapons for use in an attack. But the surveillance was reportedly called off after it turned up nothing more than drug-dealing in a Berlin park and a bar brawl.

Amri is said to have entered Germany last year and was due to be deported in June but stayed because there was a delay in receiving paperwork from Tunisia.

He had a history of crime, serving four years in an Italian prison for arson and convicted in absentia in Tunisia for a violent robbery.

A police notice lists six different aliases used by Amri, born on 22 December 1992, who at times tried to pass himself off as an Egyptian or Lebanese.

The German authorities warn he could be armed and dangerous and are offering a reward of up to €100,000 (£84,000; $104,000) for information leading to his arrest.

It is thought Amri may have been injured in a struggle with the Polish driver of the lorry who was found murdered in the cab.

Investigators believe the lorry was hijacked on Monday afternoon when it was parked in an industrial zone in north-western Berlin pending delivery of its cargo.