NICE, France (AP) -- A truck drove onto a sidewalk for more than a mile, plowing through Bastille Day revelers who'd gathered to watch fireworks in the French resort city of Nice late Thursday.
At least 80 people were killed and 18 critically ill, authorities said, and some officials and witnesses called it a deliberate attack.
The ranking politician of the Alpes-Maritime department that includes Nice said the truck plowed into the crowd over a distance of 2 kilometers (1.2 miles), killing 80 people and wounding 50. 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."
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.
Wassim Bouhlel, a Nice native who spoke to the AP nearby, said that he saw a truck drive into the crowd. "There was carnage on the road," he said. "Bodies everywhere."
The president of the Provence Alpes C(te d'Azur regional council, which includes Nice, 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."
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 was to end July 26. The decision needs parliamentary approval.
"The terrorist character (of the attack) cannot be denied," he said.
Alpes C(te d'Azur regional council, which includes Nice, 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."
Bouhlel said he witnessed the man emerge with a gun and start shooting.
Images being broadcast across French media showed revelers 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.
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.
France's ambassador to the United States, Gerard Araud, characterized the events as a "terrorist attack."
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.
Obama's full statement:
"On behalf of the American people, I condemn in the strongest terms what appears to be a horrific terrorist attak in Nice, France, which killed and wounded dozens of innocent civilians. Our thoughts and prayers are with the families and other loved ones of those killed and we wish a full recovery for the many wounded.
"I have directed my team to be in touch with French officials and we have offered any assistance that they may need to investigate this attack and bring those responsible to justice. We stand in solidarity and partnership with France, our oldest ally, as they respond to and recover from this attack.
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."