French police were hunting a man who had appeared to drive his car at a group of soldiers jogging outside their base in the foothills of the Alps on Thursday, authorities said.

It was not clear if the driver had sought to run down the 10-strong group from the 93rd Mountain Artillery regiment or simply scare them, a spokesman for the local prefecture said.

The incident caused alarm in a country on edge after an Islamic State loyalist went on a rampage in southern France last Friday, killing four people in the first militant attack since President Emmanuel Macron lifted a state of emergency.

"We don't know if it was an involuntary action, an act to try to scare the soldiers, or a deliberate gesture," the spokesman said.

No one was injured in the incident, which took place in Varces-Allieres-et-Risset, a small town south of Grenoble.

The mayor said school children were being kept indoors while the driver remained at large, local media reported.

A source close to the investigation said the driver's motivations were unclear, but that the incident was being taken seriously.

Macron on Wednesday said France was locked in a fight against "clandestine Islamic fundamentalism" as he paid tribute to the gendarme who took the place of a hostage in Friday's attack in Trebes and was killed by the Moroccan-born assailant.