Officers said they were treating the incident as terror-related and the prime minister, Stefan Lofven, said everything indicated it was “a terror attack”.
The capital was immediately locked down as police set up barricades, suspended public transport and warned people to avoid the city centre. Police later evacuated the central train station close to where the attack took place.
Photos on social media showed the truck crashed into the corner of the Ahlens upmarket shopping centre with its cab on fire.
Witnesses reported people screaming and fleeing from the scene. There were also reports of gunfire, but these have not been confirmed. Hundreds of people were seen in video footage fleeing Sweden’s largest pedestrianised street.
“We were in a store, it crashed into a window a few metres away,” one person told the Swedish broadcaster SVT. “I heard glass breaking and screams. There are a lot of police and people everywhere.”
A witness named as Anna told local Aftonbladet news: “I saw hundreds of people run – they ran for their lives. I turned and ran as well.”
Two videos emerged on social media that appeared to show two different people being detained in the area, but police said no one had been arrested in connection with the attack.