The men aged 25 and 63 were detained at the Grasse home of another recently arrested suspect, a 29-year-old Tunisian man, according to the BFMTV news channel.
This brings to six the number of people held on suspicion of being connected to Brahim Issaoui, a Tunisian who killed three in the Notre-Dame Basilica on Thursday. He came to France through Italy in October.
Nice Mayor Christian Estrosi said the attacker had repeatedly shouted "Allahu Akbar" (God is great). He also reportedly carried a copy of the Quran. An anti-terrorism investigation is underway.
The attack in Nice occurred less than two weeks after teacher Samuel Paty from a Paris suburb was beheaded by a radicalised teen. The teacher was killed after showing Charlie Hebdo's caricatures of the Prophet Muhammad in one of his classes on freedom of speech.