Shouts of "Murderers!" and "Resign!" rang out as Valls and two ministers left the seafront where a huge crowd gathered to remember the 84 people mowed down on July 14 by truck driver Mohamed Lahouaiej-Bouhlel, an AFP reporter said.
Emotions in France have been running high since the 31-year-old Tunisian rammed a 19-tonne truck into a crowd leaving a fireworks display, leaving a trail of crumpled bodies in his wake.
Opposition parties have accused the Socialist government of not doing enough to prevent the third major attack in France in 18 months.