A suspected contact of the Berlin attacker has been set free in Germany as investigations continue into possible accomplices.

No charges were brought against the 40-year-old Tunisian man, who was arrested in Berlin on Wednesday, a spokesperson for federal prosecutors said.

Officials previously announced the man’s number had been found on Anis Amri’s phone, showing he “could have been involved in the attack”.

But a spokesperson said no link was established and the man has been released.

Video surfaces of Berlin attack suspect Anis Amri

“Further investigations determined that the man who was provisionally detained isn't this possible contact person of Anis Amri, so he had to be released from custody,” Frauke Köhler said.

Amri, a 24-year-old Tunisian man, fled the scene of the attack on 19 November and was shot dead by Italian police days later in Milan.

Ms Köhler said the gun he used to fire at officers was of the same calibre as the weapon used to kill a lorry driver as he hijacked his vehicle.

Investigations have also confirmed a video of Amri pledging allegiance to Isis that was released by the group following his death to be authentic.

Amri killed 12 people and injured more than 50 more when he ploughed the lorry into a busy Christmas market.

The vehicle's automatic braking system prevented more deaths by forcibly bringing it to a stop, prosecutors said.

The hijacker fled the scene and was later identified as Amri, whose wallet, identification, phone and fingerprints were found at the crime scene.

Minutes before the attack, he reportedly sent a selfie from the cab along with a message reading: “My brother, all is well, according to God's will. I am now in a car, pray for me my brother, pray for me."

“Brother” is frequently used to address other Muslims, rather than exclusively relatives, and investigators are still working to establish who received the messages.

Berlin Christmas market lorry attack Show all 18 1 /18 Berlin Christmas market lorry attack Berlin Christmas market lorry attack Several people have been killed after a lorry drove into crowds at a Christmas market in Berlin REUTERS/Fabrizio Bensch Berlin Christmas market lorry attack 'At least nine' people have been killed and more than 50 injured. AP Berlin Christmas market lorry attack Emergency Services rush a Berlin market victim to an ambulance Associated Press Berlin Christmas market lorry attack Police cordoned off the square at Kaiser Wilhelm Memorial Church following the incident REUTERS Berlin Christmas market lorry attack Rescue workers inspect the lorry that crashed into a Christmas market close to the Kaiser Wilhelm memorial church in Berlin EPA Berlin Christmas market lorry attack Emergency crews inspect the lorry that ploughed into a Berlin Christmas market, killing at least nine people AFP Berlin Christmas market lorry attack Fire crews attend the scene of the attack AFP/Getty Berlin Christmas market lorry attack Armed police secure the site of a lorry attack at a Christmas market in Berlin REUTERS Berlin Christmas market lorry attack Crushed debris is visible beneath the wheels of the vehicle REUTERS Berlin Christmas market lorry attack An injured man is pushed to an ambulance REUTERS Berlin Christmas market lorry attack Medics attend an injured person after the lorry attack which killed at least nine and injured more than 50 people AFP/Getty Berlin Christmas market lorry attack Firefighters examine the lorry which was rammed into a Berlin Christmas market REUTERS Berlin Christmas market lorry attack A person is carried into an ambulance REUTERS Berlin Christmas market lorry attack View of the lorry that crashed into a Christmas market in Berlin, killing at least nine and injuring at least 50 people AFP/Getty Berlin Christmas market lorry attack Rescue workers push a person on a stretcher to an ambulance Getty Berlin Christmas market lorry attack Firefighters assess the damage after the lorry rammed the Christmas market, killing 'at least nine', and injuring more than 50 people AP Berlin Christmas market lorry attack Firefighters stand beside a toppled Christmas tree at the site of the suspected terrorist attack in a Berlin Christmas market AP Berlin Christmas market lorry attack Damaged stalls at the scene of the incident at a Berlin Christmas market where at least nine people have been killed EPA

​The 24-year-old Tunisian man had a lengthy criminal history, including armed robbery in his home country and arson in Italy, where he was jailed for four years after arriving in Europe by boat in 2011.

Amri’s brothers believe he was radicalised during his imprisonment, travelling onwards to Germany where he became part of an Islamist network including two hate preachers in Dortmund and Hildesheim who have since been jailed for supporting Isis.

Having flagged as a terror risk, he was put under surveillance over a separate attack plot in March but the investigation stopped in September after uncovering drug dealing and minor crime but failing to reveal evidence of extremism.

Security services rated Amri as a “five” on an eight-point danger scale, Süddeutsche Zeitung reported, despite having evidence he volunteered to commit a suicide bombing and researched making explosives, and updating his file just five days before the Berlin attack.

Amri’s asylum application was denied in June but Germany was unable to deport him because Tunisia refused to accept the expulsion without documents proving his nationality.

Prosecutors in North Rhine-Westphalia also opened a fraud investigation after Amri was suspected using two of at least eight identities he employed in Germany to claim refugee benefits in two towns.