The incident is said to have occurred at 6 pm on Thursday evening, and the police write on their website that it is a suspected attempted murder in Vivalla, in Örebro.
A man in his 30s has sustained "serious injuries after being subjected to a serious assault", according to the police.
Another person, a man in his 20s, is said to have been injured in the incident.
His condition is not considered life-threatening.
Some form of shelter must have been used, the police state without leaving any further details.
The apartment where the incident is said to have occurred has now been cordoned off.