Results of a post-mortem examination on the Berlin Christmas market attacker Anis Amri indicate he was a frequent drug user, an Italian official has said.

Amri, who ploughed the lorry into a busy Christmas market on 19 December and was subsequently shot by police, was a frequent user of both cocaine and hashish.

The official said it was not possible, however, to determine whether Amri had used the drugs before the massacre that killed 12 people and injured dozens more.

Amri had fled the scene following the attack, but was later identified after his wallet, identification, phone and fingerprints were found at the crime scene.

The 24-year-old failed Tunisian asylum seeker was killed four days later during a routine stop by police in a Milan suburb.

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

Amri was found to be drug dealing when he was placed under surveillance as a potential terror risk several months prior to the attack, during which officers failed to uncover evidence of extremism.

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 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.