Seven men and one woman will go on trial on Monday over the 2016 Bastille Day attack in the French city of Nice, which saw 86 killed and hundreds injured by a gunman who drove a heavy truck into a crowd gathered to watch fireworks.

The gunman, responsible for one of the deadliest massacres in peacetime France, was shot dead by police on the spot, ending an assault that shocked a country already reeling from the Islamist attacks in Paris the previous year.

Prosecutors say the accused, who face between five years in jail to a life sentence, helped 31-year-old Tunisian-born Mohamed Lahouaiej Bouhlel get weapons, rent the truck or survey the route he took for his deadly rampage.

Lahouaiej Bouhlel swerved his truck through crowds on a stretch of about two km (1.2 miles) on the Promenade des Anglais, Nice's sea-side, palm tree-lined boulevard, causing devastation and chaos among the 25,000 people or so gathered for the festivities.

Islamic State claimed responsibility a few days later, but offered no proof that the attacker, who had a record of domestic violence and petty crimes, had direct contact with the group.

"It (the trial) will help some move forward, others are so angry that the trial won't do much for them," said Jean-Claude Hubler, who chairs the Life for Nice victims' association.

Hubler, who had been holidaying in the region with his family, was physically unharmed but witnessed the attack and tried to help others in the aftermath, including holding an injured woman's hand until the moment she died.

Three of the accused, allegedly close friends of the attacker, are accused of participation in a terrorist criminal association for helping him obtain weapons and the truck. Two of them face 20 years in jail, while the other faces a life sentence.

The five other defendants are accused of helping him indirectly through arms trafficking, but are not charged with terrorism, and face shorter sentences. One of them will be tried in absentia.

The trial will take place in the central Paris courtroom that was specially built for the November 2015 attacks case. As many among the 850 plaintiffs are Nice-based, the trial will be broadcast there too. The verdict is expected in December.

"The attacker is dead. Those who played a secondary role will be sanctioned," said Hubler, adding that he and a number of other victims were more interested in seeing whether some officials will, separately from this trial, face sanctions for what he said was a lack of security to protect the Bastille Day celebrations that day.

"This attack should basically not have happened," he said.