Paris Prosecutor Francois Molins said there were 10 children and teenagers among the dead, with 52 people in critical condition and 25 on life support.
French President Francois Hollande said the dead include a number of foreigners.
Witnesses described how the driver of the lorry sped along a promenade packed with spectators leaving a fireworks display marking France’s national holiday.
At the site of tragedy in Nice
President Hollande said the killings were a terrorist act as he extended a state of emergency in France for a further three months.
French authorities are trying to determine if the attacker — Tunisian 31-year-old Mohamed Lahouaiej Bouhlel — acted alone or with accomplices tied to Islamist terrorist organisations.
“Although the attack has not been claimed, this sort of thing fits in perfectly with calls for murder from such terrorist organisations,” prosecutor Molins said.
The French authorities are now faced with an enormous security challenge: how do they prevent another Nice-style atrocity?
Interior Minister Bernard Cazeneuve said that the truck driver Mohamed Bouhlel appeared to have been radicalised very quickly, suggesting that it was impossible to apprehend him in time.
The far right National Front, which is growing in popularity and is particularly popular in southern France, have dismissed the authorities’ approach, saying the war on Islamic extremism has not even begun.
Mr. Cazeneuve stated that it is the methodology which has changed in terror attacks that makes them so difficult to counter.
“The celebrations of July 14th were prepared in close co-operation with the city of Nice, just like we do with any other city of France. But this kind of hateful attack is so new, as the suspect didn’t use heavy guns or explosives, that it couldn’t be prevented,” Cazeneuve said.
Analysts point to a change in the profile of extremists: according to a recent Europol study, some 80 percent of Islamic State recruits have criminal records and some 20 percent were diagnosed with mental health issues.