The corpse was found in the apartment in Upplands Väsby, north of the capital, at lunchtime on Tuesday. A relative made the discovery. Police immediately suspected that the death was caused by foul play.
Four people were taken in for questioning shortly after the body was found.
Stockholm Police spokesman Stefan Anering said that the four were arrested.
“They are four teenagers. They have been taken to Sollentuna Police Station,” he said. He would not say what made police link the youths to the dead man.
Another police spokesperson, Towe Hägg, said that the four were suspected of murder or manslaughter. She said that police were speaking to local residents and carrying out a forensic examination of the apartment.