The man leapt from the vehicle just before it was destroyed by fire in Granada Road.
Eyewitness Antonia Lovell said: The car spontaneously burst into flames.
' The driver escaped before the fire and two small explosions ripped through the car. Fire Services and Police attended the incident. I saw a policeman talking to the shocked and stunned driver.'
Portsmouth City Council said the stretch of Granada Road at its junction with St Helens Parade was shut during the incident this morning, but reopened at around midday.