Self-proclaimed Islamic State claimed responsibility for the terror attack in the French Mediterranean city of Nice, which killed 84 and injured 202 during a firework display to mark France's Bastille Day latelast Thursday night.

In Paris the Public Prosecutor, Francois Molins, said five people associated with Mohamed Lahouaief Bouhlel, the truck driver who mowed down men, women and children before being killed in a gun battle with police, had been detained and were being interrogated.

Self-proclaimed Islamic State, through its news service Amaq, claimed responsibility for the attack, describing Bouhlel as one of its "soldiers," and said France was a target because of its role in attacking IS targets in Syria and Iraq.

Police also arrested Bouhlel's ex-wife in the hours after the attack, one of the five in custody..

Officers found two automatic pistols, two Kalashnikov assault rifles, two US-made M16 rifles, ammunition and a grenade in the cab of the rented truck, which came to a stop riddled with bullets after careering and zigzagging through the crowds for two kilometres along the chic Promenade des Anglais.

They also found a mobile phone and identity documents, and Molins said intelligence services were carefully sifting through the data found on the mobile phone.

Of the injured, 52 were listed as critical and of that group, 25 are on life support, hospital officials said.

The Chinese consulate in Marseilles, along the Cote d'Azur, told China Daily that two Chinese nationals injured in the attack are still being treated in hospital but are stable and out of danger.

Tuo Yannan in Paris also contributed to the story.

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