During the night towards Friday, the police and ambulance were alerted to Östermalm in Stockholm.
A seriously injured man had been found on the street.
The injured man was cared for on site by medical staff and taken by ambulance to hospital where he then died.
Technical examination to wait
"The circumstances surrounding the death are unclear and to find out if the man has been the victim of a crime, the police have initiated a preliminary investigation into the murder," the police write on their website.
During the day, the police will conduct a technical investigation of the site.
Relatives have not been notified as the man has not yet been identified.