The fifth man was taken into custody in the small hours of Monday morning, according to police inspector Lars Hamrén.
Two men are being held on suspicion of murder, while two men and a woman are suspected of being accomplices to the crime or of harbouring criminals.
All five, along with the murder victim, were previously known to the police, said Hamrén.
Police went to the apartment on Saturday after a tip-off. Two people who were outside the building at the time were taken to the police station for questioning and were held on suspicion of involvement.
The other arrests followed and were ‘undramatic’, said Lars Hamrén.
The victim’s injuries indicated that he had been subjected to violence, but it was still unclear on Monday morning how he was murdered.
Police will continue to question those in custody on Monday.