The accident happened just after 7am on Saturday, when a truck collided with a car on the E4 motorway.
The three people who died were travelling in the car, according to Umeå police. A fourth person in the car was seriously injured.
There were three people in the truck at the time and they were all slightly hurt. All of the injured people have been taken to Skellefteå hospital.
The cause of the accident is still not clear. The car which the three victims were travelling in was not Swedish-registered, say the police.
The E4 was reopened at around 10.30am.
In another accident in the north of the country, a 22 year old Norwegian man died and four others of a similar age were injured in an accident northwest of Arvidsjaur on Friday night.
The five friends were on their way to the Trästock festival in Skellefteå, according to Luleå police.
The car, driven by the 22 year old, careered off the road 95 and hit a tree.
The passengers – one man and three women – were taken to Sunderbyn hospital for treatment. They are said to be in a serious but stable condition.