Prosecutors have stated that the suspects, who are French and Tunisian, had links to the attacker, 31 year-old Mohamed Lahouaiej Bouhlel and they were detained on Monday in the Alpes-Maritimes region, which includes Nice.
It was stated that at least five others already face preliminary terrorism charges accused of helping Bouhlel to get a pistol and of providing other forms of support and Bouhlel, who was shot dead by police, was a Tunisian with French residency.
He has driven a truck through a crowd that had assembled for a fireworks display on Nice's Promenade des Anglais, killing 86 people and injuring a further 434. Islamic State has claimed responsibility for the attack on 14th July.
But while the French authorities have said Bouhlel had been inspired by IS's propaganda, they have said they had not found anything to show that the group actually orchestrated the assault.
