Berlin authorities may have known that a Christmas market terror attack was being planned days before it took place, it has been reported.

A 23-year-old Pakistani asylum seeker named as Naved B, who entered the country under a false name, was arrested on suspecion of murdering 12 and injuring dozens by ploughing a lorry into crowds gathered outside the Kaiser Wilhelm Memorial Church last night.

However, there are reports in Germany that police now believe he was not the perpetrator and that the true attacker is 'still armed, at large and can cause fresh damage.'

According to security sources, authorities in the German capital had information in recent days about a possible attack against a Christmas market.

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Berlin authorities may have known that a Christmas market terror attack was being planned days before it took place, it has been reported

First picture: A 23-year-old named as Naved B, who entered the country under a false name on New Year's Eve 2015, is shown here being bundled into a police van after his arrest

The claim was shared on Twitter by Clemens Wergin , the Washington bureau chief for the German newspaper Die Welt

In late November, the US State Department issued a warning to its citizens to be cautious during 'holiday festivals, events and outdoor markets'

The claim was shared on Twitter by Clemens Wergin, the Washington bureau chief for the German newspaper Die Welt.

ISIS had, in recent weeks, had made renewed calls for disciples to carry out atrocities in Europe and German intelligence warned Berlin authorities recently that the city's bustling markets - tourist magnets for foreigners - were vulnerable to attack.

On July 14, a truck ploughed into Bastille Day revellers in the southern French city of Nice, killing 86 people. ISIS claimed responsibility for that attack, which was carried out by a Tunisian living in France.

Officials of the Office for the Protection of the Constitution, the BfV, had for long warned of potentially hundreds of terrorists disguised as refugees making it to Germany hidden among real migrants.

In late November, the US State Department issued a warning to its citizens to be cautious during 'holiday festivals, events and outdoor markets'.

A suspected radical Islamic attacker murdered 12 and injured dozens by ploughing a lorry into crowds gathered at a market outside the Kaiser Wilhelm Memorial Church last night

Floral tributes have been left close to the scene after a truck ploughed into a crowded Christmas market outside the Kaiser Wilhelm Memorial Church in Berlin

The warning said: 'Credible information indicates the Islamic State of Iraq and the Levant, al Qaeda, and their affiliates continue to plan terrorist attacks in Europe, with a focus on the upcoming holiday season and associated events.

'US citizens should also be alert to the possibility that extremist sympathisers or self-radicalised extremists may conduct attacks during this period with little or no warning.'

Police say the 32 ton truck smashed the wooden stalls of the market to matchwood and crushed people caught in its path next to the Kaiser Wilhelm Memorial Church.

The attacker turned off the truck's lights before mounting the pavement at 40mph and ploughing through crowds of people enjoying mulled wine after work.

The vehicle laden with steel cargo ripped through stalls and shoppers at 7pm on Breitscheidplatz Square in the German capital's main shopping area.

Witnesses said victims were sent flying like bowling pins as the killer driver steered at them before jumping out of the cab and racing from the scene. Police traced the masked terror suspect to a nearby zoo and managed to take him alive. He is in a Berlin police station today.

The truck was taken from a building site in Poland. According to the firm owner, Ariel Zurawski, the driver - his cousin - was no longer contactable after 4pm

Tributes: Flowers, candles and messages are being left at the scene of the atrocity today as German comes to terms with the terror attack

Police confirmed the lorry's original Polish driver, who was transporting steel beams from Poland to Germany, was last heard from at around 4pm yesterday and was found dead in the cab in an apparent murder hijacking.

German officials had earlier said that the driver was a Pakistani national who entered Germany via the Balkans between December 31 and February as an asylum seeker. He was believed to be living in a refugee camp at Berlin's Tempelhof airport, which was raided by an elite group of armed anti-terror police at 4am this morning.

Counter-terrorism authorities also warned of the risk that refugees could be targeted by extremist recruiters weeks before the Berlin Christmas market carnage.

The threat was highlighted in a report published by Europol, the EU's law enforcement agency, at the start of this month. It also cited unconfirmed reports that German authorities were aware of hundreds of attempts by jihadists to recruit refugees.

The Europol report said: 'Elements of the (Sunni Muslim) Syrian refugee diaspora may become vulnerable to radicalisation once in Europe and may be specifically targeted by Islamic extremist recruiters.'

German chancellor Merkel, 62, has come under huge political pressure for allowing nearly a million people fleeing conflict and poverty in the Middle East and Africa to arrive in the country this year and last

A tow truck operates at the scene where a truck ploughed through a crowd at a Christmas market on Breitscheidplatz square near the fashionable Kurfuerstendamm avenue in the west of Berlin

Last night, questions were being asked about why German authorities had not done more to protect people in Berlin - having had information about a potential threat. German Chancellor Angela Merkel is pictured yesterday

There is no firm evidence that terrorist travellers 'systematically use the flow of refugees to enter Europe unnoticed' but it is indisputable that some have entered the EU posing as refugees, the paper added.

It said: 'According to unconfirmed information, German authorities were aware of around 300 recorded attempts made by jihadists to recruit refugees who were trying to enter Europe by April 2016.'

Germany, the UK, France, Belgium, and the Netherlands were identified in the assessment as being 'high on the target list' for ISIS aggression.

Last night, questions were being asked about why German authorities had not done more to protect people in Berlin - having had information about a potential threat.

Security expert Professor Anthony Glees, of Buckingham University, told Sky News: 'Forgive me for saying this on such a tragic evening, it is mealy-mouthed to tell individual citizens to be careful when they go to Christmas markets.

'It is the job of the state and agencies of the state, the intelligence of security agencies, to keep people safe.

Police say the 32 ton truck smashed the wooden stalls of the market to matchwood and crushed people caught in its path next to the Kaiser Wilhelm Memorial Church

A witness to the atrocity spotted a man escaping from the scene, at Breitscheidplatz Square, outside the Kaiser Wilhelm Memorial Church, and gave chase

German police were able to capture the Berlin lorry attacker so quickly thanks to a hero witness who tracked the killer when he fled from the scene, it has emerged

'If there was clear intelligence that a Christmas market was going to be attacked, then all Christmas markets should have been shut until that danger was dealt with. You cannot tell people to watch out for a truck that might be driven by terrorists in their direction. You cannot do it that way.'

Berlin's top security official has since called for Christmas markets in the city to remain shut today.

Germany's Interior Ministry says Berlin's state interior minister, Andreas Geisel, told federal and regional counterparts that operators of Christmas markets in the capital were asked to close out of respect for the victims and their relatives.

But the ministry says the officials agreed that Christmas markets and other major events across Germany should go ahead and that decisions on tightening security measures should be made locally.

The federal interior minister, Thomas de Maiziere, said: 'Whatever we find out going forward about the exact background motive of the perpetrators, we must not and will not allow our free life to be taken away.'

Meanwhile, police forces across Britain have stepped up security at Christmas markets this year in a bid to prevent ISIS-inspired terror attacks such as the one in Berlin.

The security services warned the UK was at risk of terror attacks on 'large crowds of soft target civilians' by the likes of ISIS and al-Qaeda during the festive season.

Eleven forces are sending out anti-terrorism police patrol squads to shopping centres, transport hubs and tourist hotspots in a bid to spot extremists carrying out 'hostile reconnaissance'.

It emerged last week that 200 undercover SAS soldiers are to be deployed on Britain's streets to assist police forces in the event of an attack.