A boy in his mid-teens was found on Wednesday evening with injuries from a sharp object, after the police were alerted to S:t Göransparken in central Uppsala.
He was treated by paramedics and taken to hospital. According to the police, he does not have life-threatening injuries.
With the help of information from witnesses, three boys, also in their mid-teens, were arrested soon after. They are now suspected of aggravated robbery.