A truck have crashed into a department store Ahlens at Drottninggatan in the central of Stockholm, Sweden April 7, 2017.

A truck crashed into an upscale department store in central Stockholm on Friday, and Swedish radio says the crash has killed four people and injured 12. People in the downtown area are fleeing the scene in panic.

Swedish PM said “Sweden has been attacked, everything indicating it is an act of terrorism.”

Swedish broadcaster SVT says shots have been fired at the scene and the Swedish news agency TT says several people have been rushed away in ambulances.

Live television footage on Friday showed smoke coming out of the upscale Ahlens department store on Drottninggatan Street, which the truck smashed into. The department store is part of Sweden-wide chain. The building includes several stores at street-level.

Swedish police have issued images of the truck driver of the attack, they showed a picture of a man wearing a grey hoodie and said they were looking for him.

Swedish police said they have arrested one person in connection with a deadly truck attack in central Stockholm.

“One person has been arrested who may be connected with the incident,” police said in a statement.

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.

It was not immediately clear whether it was an accident or an attack.

“We stood inside a shoe store and heard something … and then people started to scream,” witness Jan Granroth told the Aftonbladet daily. “I looked out of the store and saw a big truck.”

Swedish police confirmed that a truck drove into people and the store but could not confirm the reports of shots fired. Police said in a statement “there are reports of injured but we have no details on how many and how serious.”

A truck have crashed into a department store Ahlens at Drottninggatan in the central of Stockholm, Sweden April 7, 2017.

A truck have crashed into a department store Ahlens at Drottninggatan in the central of Stockholm, Sweden April 7, 2017.

A truck have crashed into a department store Ahlens at Drottninggatan in the central of Stockholm, Sweden April 7, 2017.

This slideshow requires JavaScript.