Four-year-old Kassim Benouali and little brother Sadek, two, died inside a car that may have reached 70C during the scorching heatwave in France

Tragic new details have emerged about the death of a three-year-old boy who passed away in his family's car during a heatwave that has scorched France.

The boy climbed into the unlocked car while out of his parents' sight; his mother was hospitalised in shock. Two other children died in Carpentras on Monday.