Around 02:00 on Saturday morning, a charge detonated outside the health center on Södergatan in central Helsingborg.
Two window panes were smashed and a small fire broke out in the premises as a result of the detonation.
According to information to SVT, a man in his 40s has been seriously injured in connection with the fire and taken to hospital.
Rescue services with smoke divers are on site and are trying to put out a fire that started on the basement level as a result of the explosion.
The police have set up large roadblocks on Söder in Helsingborg.