Some form of explosive charge detonated shortly after midnight on Monday morning in a gate of a multi-family house in Segeltorp in southern Stockholm.
A window has been shattered and there is some damage to the gate, says Ola Österling, press spokesperson for the Stockholm police, about the incident that the police received an alarm about half an hour after midnight.
There are no reports of personal injuries.
Interrogations are being conducted while, among other things, bomb technicians are examining the site. An investigation into suspicion of general endangerment has been initiated.