A woman was found badly injured in Frölunda, in Gothenburg, just before midnight.
How the injuries occurred is currently unclear, but a preliminary investigation into attempted murder or manslaughter has been established.
The woman was taken to hospital with serious injuries.
One person has been arrested on suspicion of the crime.
Two more attempted murders
During Thursday evening, the police were called to a place in central Vara where two women were arguing and where one is suspected of having tried to strangle the other.
The woman is taken to hospital for treatment
Around 5:20 on Friday morning, a man came into Uddevalla hospital with stab wounds to his body.
The man is suspected of having been the victim of an attempted murder in central Uddevalla.
After locating the likely crime scene, a man in his 30s was arrested as he tried to hide behind a container.
The text is updated