The police website said a bomb squad was on its way to the scene, where windows were broken in some buildings. “Police are investigating what happened. It is not known whether anyone has been injured,” police said.

Swedish public radio reported that a large blast had destroyed the windows and balconies of a five-storey residential building and damaged other buildings.

A spokeswoman at Linkoping University Hospital said several people had been taken to hospital after the incident.

Photos published by tabloid Aftonbladet showed two multi-storey buildings with shattered windows and wrecked balconies, with some damage to their roofs also visible.

Police said in a statement that several blocks around the area had been cordoned off but that there were no plans to evacuate residents.

While the cause of the apparent explosion was not clear, Sweden has seen several cases in recent years where explosives were used in suspected gang-related attacks.