IS has claimed responsibility for the lorry attack which killed at least 84 people during Bastille Day celebrations in Nice.
An Islamic State-run media outlet on Saturday said, “The person who carried out the operation in Nice, France, to run down people was one of the soldiers of Islamic State. He carried out the operation in response to calls to target nationals of states that are part of the coalition fighting Islamic State.”
French authorities said they were checking the claim.
Five people have been arrested since the attack.
The driver’s estranged wife is also being held.
Mohamed Lahouaiej Bouhlel, a French-Tunisian was described as a “weird loner” who “became depressed” when his wife left him.
He lived in the Riviera city where he drove a heavy-goods vehicle through a crowd that had gathered to watch the display on Nice’s Promenade des Anglais.
The promenade was re-opened on Saturday morning as France began three days of national mourning and President Hollande held a security meeting with ministers, police and intelligence officers.
Many continue to leave floral tributes at the metal barriers lining the promenade.