The truck driver who killed at least 84 people when he ploughed into a crowd on Bastille Day in Nice was a 31-year-old Franco-Tunisian born in Tunisia, a police source says.
Interior Minister Bernard Cazeneuve said 80 people had died and 18 were in a critical condition after the terror attack in the southern French city. The ministry later updated the death toll to 84.
Many more were also wounded in the attack along the famed seafront Promenade des Anglais as Bastille Day fireworks ended just after 10.30 pm (11am NZT).
The driver also opened fire before police shot him dead, Reuters reported.
In a pre-dawn address to the nation, President Francois Hollande said he was calling up military and police reservists to relieve forces worn out by an eight-month state of emergency begun after the Islamic State militant group killed 130 people in Paris.
He extended the state of emergency by three months.
"France is filled with sadness by this new tragedy," Mr Hollande said, noting several children were among the dead in what he said he had no doubt was an act of terrorism.
He called the carnage, which came as France celebrated the anniversary of the 1789 revolutionary storming of the Bastille, an attack on liberty by fanatics who despised human rights.
France would, nonetheless, continue military operations in Syria and Iraq.
Counter-terrorist investigators were seeking to identify the driver. A local government official said weapons and grenades were found inside the unmarked articulated heavy truck.
Officials said hundreds were hurt as the driver wove along the seafront, knocking them down "like skittles".
The attack, which came eight months and a day after Islamic State gunmen and suicide bombers struck the French capital on a festive Friday evening, seemed so far to be the work of a lone assailant.
Newspaper Nice-Matin quoted unidentified sources as saying the driver was a 31-year-old local of Tunisian origin. Reuters later reported the same, from a police source.
The man had reportedly been known to the police for common crimes but not to the intelligence services.
Police were working to establish what accomplices he might have had in a city with a reputation for Islamist activism.
There had been no claim of responsibility made almost six hours after the attack.
'I've never seen anything like it'
Tony Molina, a tourist from California, told CNN he saw the incident unfold from the balcony where he had been watching the fireworks.
"We looked out and saw this white panel truck ploughing into people.
"It was just crazy. I've never seen anything like it, it is unbelievable.
"They were screaming and running everywhere."
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.
Social media had earlier carried images of people lying apparently lifeless in pools of blood.
Hours before the attack, Mr Hollande, who was in the south of France at the time, said the state of emergency put in place after the Paris attacks in November would not be extended after it expired on 26 July.
"We can't extend the state of emergency indefinitely, it would make no sense. That would mean we're no longer a republic with the rule of law applied in all circumstances," Mr Hollande had told journalists in a traditional Bastille Day interview.
- Reuters / BBC / CNN