Witnesses, speaking to local media, said they had seen people on the ground after the truck crashed.
Photographs from the scene also showed a number of people injured.
“There is total confusion, I do not know how many are injured, many people are totally shocked,” Leif Arnmar, who works in Ahlens department store, told Swedish national broadcaster SVT.
“We were in a store, it crashed into a window a few meters away,” another person told the Swedish broadcaster SVT, in a translation provided by The Guardian. “I heard glass breaking and screams. There are a lot of police and people everywhere.”
An eyewitness identified as Anna, speaking to the Aftonbladet newspaper, said: “I saw hundreds of people running. They ran for their lives — I turned and ran as well.”
Another called Durde, also speaking to Aftonbladet said: “The lorry just drove, full speed ahead, down Drottninggatan.”
Jan Granroth, who was shopping in the area, added: “We were inside a shoe store and heard noise. I looked out from the store to see this huge truck slam into the wall on the opposite side of the street.”
— Francis Whittaker and Rose Troup Buchanan