Swedish police said explosives were used, but ruled out terrorism.

The explosion occurred on Monday outside the entrance to a building housing a business and several apartments and led to the evacuation of dozens of apartments. It could be heard several kilometres away.

Stockholm police chief Erik Widstrand said it was "one of the most powerful we have had in the region".

He added that terror was not suspected and no one has been arrested.

Sweden has in recent years seen explosions and shootings linked to feuding gangs, and Monday's episode could be linked to that.

Widstrand said forensics were working on establishing what kind of explosives were used.

Several residents told Swedish media that they were awakened by a loud explosion.

Australian Associated Press