It must have started as a fight at a restaurant, the police state on their website.
Several people were involved and a 25-year-old man is said to have received serious knife injuries.
He is now being treated in hospital.
Another person is said to have been slightly injured.
- It is about two men who were in a restaurant in Tumba and they somehow started arguing with two other men and it ended with the younger man being seriously injured with a knife and the other being slightly injured, says Anna Westberg, the police's spokesperson.
Investigating attempted murder
The police are investigating the incident as attempted murder.
Later in the evening, a powerful explosion occurred in an industrial area, also in Botkyrka municipality.
According to Aftonbladet, the police do not believe that there is any connection between the events.
The article is updated