A man in his 40s has been arrested on suspicion of murder and two counts of attempted murder, the Swedish news agency, TT, has reported.
According to Swedish newspaper, Aftonbladet, the dead man was attacked with a knife during a dinner party, although the police have not confirmed this.
The accused man grabbed a knife and stabbed it in the chest of the man who sat opposite him, according to the newspaper. Reportedly, the man died immediately.
The alleged attacker then attacked several people in different houses, probably with a knife, in a residential area in Forsbäck on the Onsala peninsula, just south of Kungsbacka in Halland. It is not thought the man chose the houses randomly.
Three people were taken by ambulance to Sahlgrenska University Hospital in Gothenburg. One of them was a 40-year-old man who died from his injuries. The other two are "very seriously injured," according to police.
When asked if the attack was the result of a Christmas dinner party that spiralled out of control, Johan Johansson, duty officer of the Halland police said it was possible: "We have heard that and it is not illogical given what has happened, but we have to investigate."
The attacker, who, Aftonbladet reported, is thought to be mentally ill, was known to the victims but is not thought to have been in trouble with the police before.
Onsala is a wealthy area 45kms south of Gothenburg with more than 11,000 residents. The Onsala peninsula is the largest in Sweden. It is home to the Onsala Space Observatory.