Nice attack undeniably of terrorist nature: France's Francois Hollande

French President Francois Hollande said Thursday's lethal attack on the southern city of Nice was clearly a terrorist assault and that the state of emergency imposed since a previous attack on Paris in November 2015 would be extended for another three months.

Speaking after an emergency meeting in the early hours of Friday morning, Hollande said at least 77 people were killed in an attack in which the assailant drove a big truck at high speed into dense crowds who were watching a fireworks display on the country's national Bastille Day holiday.

"There's no denying the terrorist nature of this attack of yet again the most extreme form of violence," the French leader said in a national television address at 4 a.m. (0200 GMT), about five or six hours after the carnage in Nice. 

Newspaper Nice-Matin quoted unidentified sources as saying the driver was a 31-year-old local of Tunisian origin. The truck careered for hundreds of metres along the famed Promenade des Anglais seafront, slamming into spectators watching the fireworks, listening to an orchestra or strolling above the beach towards the grand, century-old Hotel Negresco.

Live Updates | France: Truck attacker kills at least 80 in Nice Bastille Day crowd in Nice