A Moroccan-born man who stabbed a French mother and her three young daughters at an Alpine holiday village said he had been offended after the father "scratched his inner thigh" in the presence of his wife, according to the prosecutor.

He also reportedly shouted "Allahu Akbar" (God is great) three times when questioned after Tuesday's attack.

The 37-year old was arrested at the Alpine resort of Garde-Colombe, near Laragne, in southern France.

The youngest girl, aged 8, was rushed to hospital in Grenoble with a punctured lung. Her mother, 46, and sisters aged 12 and 14, were being treated at the hospital in Gap, closer to the scene of the attack. Their injuries were serious but not life-threatening.