A hunt was underway for the driver who insulted another group of soldiers after the aborted attack in Varces-Allieres-et-Risset, near Grenoble, before speeding off, the sources added.

The incident comes with France on edge after a jihadist rampage in the southwest last week, where a 25-year-old radicalised gunman killed four people, including a policeman who took the place of a hostage in a supermarket siege.

On Thursday, the four victims of the attack in the town of Carcassonne and nearby Trebes, including the heroic officer Arnaud Beltrame, will be laid to rest in the region.

Paying tribute to the officer at a national ceremony in Paris on Wednesday, President Emmanuel Macron said his act of supreme self- sacrifice would "remain etched in French hearts".