About 25 people were taken to hospital after an explosion damaged a residential building in the Swedish city of Gothenburg early on Tuesday, public service radio SR reported.
Police said they had opened an investigation. The Sahlgrenska University Hospital spokesperson said three women were seriously injured among the people taken to hospital.
Emergency services said they were working to evacuate people and put out fires in the building.
"Several apartments and stairwells are affected. It is at present unclear what has caused the explosion," the emergency services for the wider Gothenburg area said.
A spokesperson for the emergency services said that several hundred people had been evacuated from the vicinity of the explosion and fire.
The immediate cause of the explosion and fire was unclear. The Nordic country has contended with surging gang crime in recent years, with rival groups employing explosives and firearms to settle scores.

Trump says Iran deal 'largely negotiated', dispute over strait reopening
Suspect dies after trading gunfire with officers near White House
At least 90 dead in China's worst coal mine disaster in over 16 years
Rubio touts US energy on India trip meant to repair ties
Israeli strike kills five Gaza police officers, police say