Several are also seriously injured, including a young child.
The car had come from Öckeröleden, and when it entered the roundabout, it exploded for an unknown reason.
Janne Wolltin, who witnessed the explosion told TT, "When I came to the Torslanda roundabout, there was a horrible explosion. The roof of the car ahead flew up in the air."
Rescue services, several police patrols and a helicopter are at work, and technical experts were on the way to examine the car.