The third victim was a 48-year-old woman who died when the car veered off the track following a sharp bend, after it had crossed the finishing line at the race in Guimaraes.
Eight people were injured and two of them are in a critical condition, emergency services said: a 40-year-old man with head trauma and a woman of 18 with leg fractures. They were rushed to a hospital in Braga.
The driver of the car has been taken to hospital suffering from shock.
The accident happened shortly after the start of the first stage of the rally at a part of the track that was not protected by barriers. The event was suspended after the tragedy.