German police said on Sunday that they had arrested a 21-year-old man on suspicion of planning a militant attack, and linked his case to that of a second suspect in Vienna.

Special forces police arrested the man and a woman during a raid on an apartment in the western city of Neuss on Saturday, a spokesman for the Criminal Investigation Office (LKA) said.

The woman, identified in media reports as the man's wife, has been released.

German authorities have been on high alert since a failed asylum seeker from Tunisia rammed a truck into a Christmas market last month in Berlin, killing 12 people.

Dashcam footage captures the moment truck crashes into the Berlin Christmas market

Germany's Focus magazine said the man arrested on Saturday was planning a bomb attack on police and soldiers. Both he and the suspect detained in Austria had experimented with materials to create explosives in the Neuss apartment, it said.

The Neuss arrest followed a tip-off from Austrian authorities, said Frank Scheulen, spokesman for the LKA in the state of North Rhine-Westphalia.

The man, whose nationality was not given, was arrested on suspicion of planning to carry out a "serious act of violent subversion," Mr Scheulen said.

A spokesman for the prosecutor's office in Dusseldorf, in charge of the case, had no immediate comment.

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 Vienna suspect, an 18-year-old with an Albanian background, was arrested on Friday on suspicion of having contacts to Islamist militants and planning an attack, Austrian police said.

A spokesman for the German interior ministry said the German Interior Minister Thomas de Maiziere spoke about the case on Friday with his Austrian counterpart, Wolfgang Sobotka.

Computers, mobile telephones and data storage devices were seized in the Neuss raid, Mr Scheulen said.