French President François Hollande will chair a meeting with his inner security cabinet to discuss the response to Thursday's attack in the French resort city of Nice, when a truck loaded with weapons ploughed through a crowd and killed at least 84 people.
Lahouaiej-Bouhlel was known to the police as a petty criminal, but was "totally unknown to intelligence services. and was never flagged for signs of radicalisation", the prosecutor added.
Islamic State has repeatedly singled out France as a prime target for its military action against the group in Iraq and Syria, and hundreds of jihadists have left France to fight in its ranks.
The culprit, who has since been named as 31-year-old Mohamed Lahouaiej Bouhlel, swerved from side to side to kill as many people as possible as he drove for a mile along the Promenade des Anglais on the seafront of the city.
The Paris prosecutor's office said Saturday that five people are in custody following the attack.
In September 2014, IS spokesman Abu Mohammed al-Adnani, suggested supporters "run (infidels) over with your car".
His father said he had suffered from depression and had "no links" to religion. "We have an individual who was not known to intelligence services". "He would become angry and he shouted. he would break anything he saw in front of him", Mohamed Mondher Lahouaiej-Bouhlel said.
"We are also shocked", he said. But neighbors in the Nice neighborhood where the Bouhlel used to live told The Associated Press his estranged wife had been taken away by police on Friday.
In Nice, the seaside streets that would normally be bustling on a summer weekend were near-deserted, with teary residents making their way to the promenade to lay down flowers in memory of the dead.
"His wife had asked for a divorce after a violent argument", said the man, who also asked not to be identified. The truck was reportedly seen "riddled with bullets".
Mr Molins said a fake pistol, fake rifles and a dummy grenade were found inside.
French authorities said they were checking the claim. "The child was dead". Some 202 people were injured; 52 are critical, of whom 25 are on life support.
It followed a march in which around 150 people gathered outside Leeds Civic Hall holding banners displaying the phrase "Je Suis Charlie" after the January 2015 attack on French satirical magazine Charlie Hebdo.
Mr Hollande described the incident as a "terrorist attack" in a sombre televised address, adding that: "France was struck on its national day. the symbol of freedom".