The victims were two adults who were travelling in the car heading south. In the northbound car were two adults and a child. According to police in Gävle all three are seriously injured and have been taken to hospital.
Both cars are registered in the Stockholm area, but two hours after the accident the identities of those who died had not yet been established.
Driving conditions in the area were described as normal for winter.
“This is the first road accident we’ve had today,” said Ulf Cornelius, Gävle police spokesman.
At least three cars collided on the E6 near Ängelholm on Sunday afternoon. Seven ambulances were sent to the scene by SOS Alarm.
According to early reports at least eight people and several dogs were travelling in the cars, and two people were said to be trapped.