What we know:
- Truck ploughed 2km into crowd in French city of Nice
- At least 77 dead and many injured
- Truck driver shot dead
- President Francois Hollande to hold crisis talks in Paris
- Reports of arms being found inside the truck
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An attacker has killed at least 77 people and injured 100 when he drove a truck at high speed into crowds watching Bastille Day fireworks in the French Riviera city of Nice, local officials say.
Police shot and killed the driver, who drove at high speed for more than 100 metres along the famed Promenade des Anglais seafront before hitting the mass of spectators late on Thursday, regional sub-prefect Sebastien Humbert told France Info radio.
Broadcaster i-Tele quoted the prosecutor's office as saying the preliminary death toll was 60.
Local legislator Eric Ciotti told France Info radio more probably had died. Other officials put the number of wounded at least 100 and possibly more.
Humbert described it as a clear criminal attack, although the driver was not yet identified. Residents of the Mediterranean city close to the Italian border were advised to stay indoors. There was no sign of any other attack.
Officials were cautious about accounts from bystanders that the lone man driving the truck had also opened fire and, amid chatter on social media of a hostage situation, police called on people not to propagate rumours that were hampering their work.
There is no hostage situation, French interior ministry spokesman Pierre-Henry Brandet told BFM TV. "I can't give you information on the man's motives yet."
One woman told France Info she and others had fled in terror: "The lorry came zig-zagging along the street. We ran into a hotel and hid in the toilets with lots of people."
Another woman told the station she was sheltering in a restaurant on the promenade with some 200 other people, where things had calmed down about two hours after the incident.
The incident comes as France remains badly shaken by November 2015 attacks which killed 130 people at the Bataclan concert hall in Paris and nightspots across the city.
President Barack Obama released a statement offering assistance to France.
"On behalf of the American people, I condemn in the strongest terms what appears to be a horrific terrorist attack in Nice, France, which killed and wounded dozens of innocent civilians," he said.
