At least three people have been killed in Stockholm after a truck ploughed into pedestrians on a busy shopping street. The police are treating the incident as a terror attack.

First pictures and a video shot by an eye-witness show the chaos that followed as people fled the scene and emergency services arrived to treat the wounded.

The incident happened outside the Ahlens shopping mall in Drottninggatan, a pedestrianised street. A video shared on social media shows people running away from the scene of the attack. The crash caused a fire to break out and fire crews arrived to extinguish the blaze.

At least eight people have been injured, according to police.

Police have surrounded the Swedish parliament which is on lockdown after the incident. The streets in the city centre are deserted after people were told to avoid the area.

Police have ordered the evacuation of the Central Train Station, which has been surrounded by heavily armed officers.

A manhunt is under way for the Stockholm attack suspect, sources told Sky News. The suspect is thought to have run in the direction of the metro station.

Police released an image of a man they would like to speak to in connection with the attack. He is described as wearing a green jacket, grey jumper and white shoes.

Stockholm truck terror streets sealed off
Normally busy streets in Stockholm city centre were sealed off near the scene of the deadly terror truck attack Anna Ringstrom/Reuters
Stockholm truck
Emergency services work at the scene where a truck crashed into the Ahlens department store on Drottninggatan in Stockholm Jonathan Nackstrand/AFP
Stockholm truck
Emergency service workers arrive to treat wounded after truck ploughed into pedestrians in Drottninggatan in Stockholm. TT News Agency/Andreas Schyman/Reuters
Stockholm truck
Emergency services work at the scene where a truck ploughed into pedestrians in Drottninggatan, Stockholm. Jonathan Nackstrand/AFP
Police officers secure the area outside Stockholm Central station, on April 7, 2017 after a truck crashed into department store Ahlens on Drottninggatan, in central Stockholm
Police officers secure the area outside Stockholm Central station, on April 7, 2017 after a truck crashed into department store Ahlens on Drottninggatan, in central Stockholm GettyImages