Police have released a man they arrested after the truck attack on a Christmas market, according to Germany's chief federal prosecutor's office.

Investigators said they had insufficient evidence to link him to the attack, which killed at least 12 people and injured dozens more.

"The investigation up to now did not yield any urgent suspicion against the accused," the prosecutor's office said in a statement.

The prosecutor's office said the suspect had made extensive statements during a police hearing, but denied the offence.

It added it had been impossible to track the truck driver by eye-witnesses following the attack and that the investigation so far had not been able to prove that the suspect was in the truck's cab at the time of the attack.

The man who was arrested, a 23-year-old Pakistai refugee named as 'Naved B', matched witness descriptions of the truck driver, but investigators have not been able to prove he was in the truck's cab at the time of the attack.

He was arrested shortly after the atrocity but denied involvement.

Police are still hunting for the attacker, who is presumed to be armed.

Under German law, prosecutors have until the end of the calendar day following an arrest to seek a formal arrest warrant keeping a suspect in custody.

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

'Naved B' was granted a temporary residence permit in June 2016, according to the Die Welt newspaper, which cited a criminal police report.

German interior minister Karl Ernst Thomas de Maizière told a press conference on Tuesday that his application for asylum had not yet been completed.