Attack on Berlin Christmas market treated as 'terrorist' by police

German police said on Tuesday they were treating as "a probable terrorist attack" the killing of 12 people when a lorry ploughed through a packed Berlin Christmas market.

Dozens more were wounded on Monday when the truck tore through the crowd, smashing through wooden stalls and crushing victims, in scenes reminiscent of July's deadly attack in the French Riviera city of Nice.

Police arrested the man believed to have deliberately crashed the heavy vehicle loaded with steel beams into the market near the capital's iconic Kaiser Wilhelm Memorial Church.

Berlin police said they presumed the lorry was "intentionally steered" into the crowd and called the bloody carnage a "probable terrorist attack".

"Our investigators assume that the truck was deliberately steered into the crowd at the Christmas market at Breitscheidplatz," police said on Twitter.

"All police measures related to the suspected terrorist attack at Breitscheidplatz are progressing at full steam and with the necessary diligence," police said.

The man behind the wheel was an asylum seeker believed to be from Afghanistan or Pakistan who arrived in Germany in February, according to security sources cited by DPA news agency.

The lorry tore through the market for as far as 80m, smashing through wooden huts selling food and drink.

On Tuesday, German Chancellor Angela Merkel - who has been criticised by far-right parties for her open-door border policies - said it would be particularly troubling if the assailant were a refugee.

"There is much we still do not know with sufficient certainty but we must, as things stand now, assume it was a terrorist attack," Merkel told reporters.

"I know it would be especially hard for us all to bear if it were confirmed that (the) person who committed this act was someone who sought protection and asylum."

Truck driver found shot dead

On Tuesday German authorities said that a Polish man found dead on the passenger seat was "shot" dead, according to AFP.

After a national telephone conference of ministers, Karl-Heinz Schroter, the interior minister of Brandenburg state, said "one of the victims was shot", without specifying whether this victim was the registered driver of the truck, the minister's spokesman.

The man, thought to have been the truck's registered driver, had not steered the vehicle, police earlier said.

"We haven't heard from him since this afternoon. We don't know what happened to him," transport company owner Ariel Zurawski told the AFP news agency on Monday. "He's my cousin, I've known him since I was a kid. I can vouch for him."

One of the survivors, Australian Trisha O'Neill, said she was only metres from "this huge black truck speeding through the markets crushing so many people".

"I could hear screaming and then we all froze. Then suddenly people started to move and lift all the wreckage off people, trying to help whoever was there," she told the Australian Broadcasting Corporation.

O'Neill said there was "blood and bodies everywhere".

"It wasn't an accident," said another visitor, British tourist Emma Rushton. "We heard a really loud bang and saw some of the Christmas lights to our left starting to be pulled down," she told Sky News.

"Then we saw the articulated vehicle going through people and through the stalls and just pulling everything down and then everything went dark."

German broadcaster rbb cited security sources as saying the arrested lorry driver came to Germany via Passau, a city on the Austrian border, on 31 December last year.

It cited the sources as saying the man was born on 1 January 1993 in Pakistan and was already known to police for minor offences. None of this has been confirmed by police.

Chancellor Angela Merkel reacted quickly, with spokesman Steffen Seibert tweeting: "We mourn the dead and hope that the many people injured can be helped."