Jonathan Nackstrand, AFP | Police cordons the truck which crashed into a department store in central Stockholm, April 7, 2017.

Four people have been killed after a truck rammed a crowd of pedestrians before crashing into a busy department store in central Stockholm on Friday, Swedish police said, in what local authorities are treating as a terrorist attack.

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At least a dozen people were also injured in the incident on Drottninggatan (Queen Street), one of the city's major pedestrian streets

Sweden's Prime Minister Stefan Lofven described the crash as an "awful terrorist attack".

"These kinds of actions will never succeed," Lofven told a news conference. "Our message will always be clear: you will not defeat us, you will not govern our lives, you will never, ever win."

Swedish PM speaks on Stockholm Attack

Police said they had arrested one person in a northern Stockholm suburb after earlier circulating a picture of a man in connection with the investigation.

In the picture, the man is seen wearing a white sweater and dark hoodie under a military green jacket.

Police say they want to speak to this man, seen here on CCTV footage.

There was no immediate claim of responsibility for the attack.

Police said security at Swedish borders had been heightened. They did not rule out the possibility other attackers were involved.

Stolen truck

The ramming occurred just before 13:00 GMT at the corner of the Ahlens department store, above-ground from Stockholm's central subway station.

Pictures showed a large blue truck with a mangled undercarriage smashed into the store.

A spokeswoman for transport company Spendrups told AFP that the truck "had been stolen during a delivery to a restaurant".

Emergency services work at the scene where a truck crashed into Ahlens department store on Drottninggatan in central #Stockholm @AFPphoto pic.twitter.com/wwkndiYI3B — AFP news agency (@AFP) April 7, 2017

Video images showed an area blocked off by police and crowds gathering around the police cordon, with thick smoke rising from the scene.

Police vans circulating in the city using loudspeakers urged people to go straight home and avoid large crowds.

Watching the events unfold after a truck drove into Åhléns on Drottninggatan. pic.twitter.com/kxJLUOAsns — Emil Stenqvist (@svammel) April 7, 2017

Helicopters could be heard hovering in the sky over central Stockholm, and a large number of police cars and ambulances were dispatched to the scene, witnesses said.

Traffic on the Stockholm metro was halted, with the attack taking place at the city's T-Centralen station, through which all the city's lines pass.

'Horror and outrage'

Friday's crash is near the site of a December 2010 attack in which Taimour Abdulwahab, a Swedish citizen who lived in Britain, detonated a suicide bomb, killing himself and injuring two others.

Abdulwahab rigged a car with explosives in the hope that the blast would drive people to Drottninggatan where he would set off devices strapped to his chest and back.

The car bomb never went off, and Abdulwahab died when one of his devices exploded among panicked Christmas shoppers.

Several attacks in which trucks or cars have been driven into crowds have taken place in Europe in the past year, including in London, Berlin and the French city of Nice.

German Chancellor Angela Merkel's spokesman said her government's "thoughts are with the people in Stockholm, the injured, the relatives, first responders and police".

In Paris, a statement by the Elysée Palace expressed the French presidency's "horror and outrage" over the attack, adding that "the unflinching fight against terrorism must remain a priority" for Europe.

EU Council President Donald Tusk said in a tweet: "My heart is in Stockholm this afternoon. My thoughts are with the victims and their families and friends of today's terrible attack."

Jean-Claude Juncker, the head of the European Commission, said "an attack on any of our (EU) member states is an attack on us all".

We stand in solidarity with the people of #Sweden. An attack on any of our Member States is an attack on us all https://t.co/YDYiHoKkSV — Jean-Claude Juncker (@JunckerEU) April 7, 2017

(FRANCE 24 with AFP, REUTERS, AP)

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