A truck loaded with weapons and hand grenades drove along a sidewalk in the French resort city of Nice for more than a mile, ploughing through Bastille Day revellers who had gathered to watch fireworks late on Thursday. At least 80 people were killed before police killed the driver, authorities said.
Nice prosecutor Jean-Michel Pretre described a horrific scene, with bodies strewn along the roadway, and Sylvie Toffin, a press officer with the local prefecture, said the truck ran over people on a "long trip" down the sidewalk near Nice's Palais de la Mediterranee, a building that fronts the beach.
A Nice native who spoke to the AP, said that he saw a truck drive into the crowd. "There was carnage on the road," he said. "Bodies everywhere." He said the driver emerged with a gun and started shooting.
France's interior minister Bernard Cazeneuve said 80 people were killed, including children, and 18 were in critical condition. The Paris prosecutor's office announced an investigation for "murder, attempted murder in an organized group linked to a terrorist enterprise".
"We are in a war with terrorists who want to strike us at any price and in a very violent way," Cazeneuve said.
The ranking politician of the Alpes-Maritime department that includes Nice said the truck ploughed into the crowd over a distance of two kilometres. Many of those on the ground were in shorts and other summer clothing.
Eric Ciotti said on BFM TV that police killed the driver "apparently after an exchange of gunfire".
The president of the Provence Alpes Cote d'Azur regional council said the truck was loaded with arms and grenades. Christian Estrosi told BFM TV that "the driver fired on the crowd, according to the police who killed him".
Images being broadcast across French media showed holiday-makers running for their lives down Nice's palm tree-lined Promenade des Anglais, the famous seaside boulevard named for the English aristocrats who proposed its construction in the 19th century.
Video footage showed men and women - one or two pushing strollers - racing to get away from the scenes. And in what appeared to be evidence of a gun battle, photos showed a truck with at least half a dozen bullet holes punched through its windshield.
It was not immediately clear who would have been behind an attack, but France has recently seen a spate of dramatic assaults by jihadist groups, including the Islamic State group which straddles Iraq and Syria.
France under threat: Hollande
President Francois Hollande said in a televised statement that all of France was under an "Islamist terrorist threat" and extended by three months a state of emergency that has been in place since the November attacks that killed 130 in Paris, which was to end on 26 July. The decision needs parliamentary approval.
"The terrorist character (of the attack) cannot be denied," he said.
Hollande said he was calling a defence council meeting Friday that brings together defence, interior and other key ministers, then heading to Nice. He listed several measures to bolster security in France after two waves of attacks last year that killed 147 people.
Besides continuation of the state of emergency and the Sentinel operation with 10,000 soldiers on patrol, he said he was calling up "operational reserves", those who have served in the past and will be brought in to help police, particularly at French borders.
US President Barack Obama condemned what he said "appears to be a horrific terrorist attack".
European Council president Donald Tusk said it was a "tragic paradox" that the victims of the attack in Nice were celebrating "liberty, equality and fraternity" - France's motto - on the country's national day.
Writing online, Nice Matin journalist Damien Allemand who was at the waterside said the fireworks display had finished and the crowd had got up to leave when they heard a noise and cries.
"A fraction of a second later, an enormous white truck came along at a crazy speed, turning the wheel to mow down the maximum number of people," he said.
"I saw bodies flying like bowling pins along its route. Heard noises, cries that I will never forget."
Graphic footage showed a scene of horror up and down the Promenade, with broken bodies splayed out on the asphalt, some of them piled near one another, others bleeding out onto the roadway or twisted into unnatural shapes.
"Help my mother, please!" one person yells out amid a cacophony of screaming and crying. A pink girl's bicycle is briefly seen overturned by the side of the road.
The origin and authenticity of the footage could not immediately be verified.
Kayla Repan, of Boca Raton, Florida, was among the hundreds gathered on the promenade to watch fireworks.
"The whole city was running. I got extremely frightened and ran away from the promenade," she said. "It was chaos".
(See: No Indians among Nice victims; Modi 'appalled')