NICE, France (CBSNewYork/AP) -- At least 80 people were killed, and dozens of others injured, in a terrorist attack after a truck loaded with weapons and hand grenades plowed into a crowd celebrating Bastille Day in Nice, France.
French Interior Minister Bernard Cazeneuve said 80 are dead in the attack, and 18 are critically injured. CBS News reported more than 50 were injured.
"We are in a war with terrorists who want to strike us at any price and in a very violent way," Cazeneuve said.
French President François Hollande said some children were among the victims in the terrorist attack.
"This terrorist attack is once again a very violent act, an absolutely violent act, and it's quite clear we must do everything to fight against the scourge of terrorism," Hollande said.
Hollande stated that France's state of emergency has been extended by three months as he will call a defense council meeting Friday that brings together defense, interior and other key ministers. 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.
The truck's driver drove on to the sidewalk and plowed for more than a mile through a crowd of revelers who'd gathered to watch fireworks in the French resort city.
"It's a scene of horror," Eric Ciotti, head of the French department in which Nice is located, told France Info radio.
Nice prosecutor Jean-Michel Pretre described a horrific scene, with bodies strewn about along the roadway.
Sylvie Toffin, a press officer with the local prefecture, said the truck "hit several people on a long trip" down the sidewalk near Nice's Palais de la Mediterranee, a building which fronts the beach.
Toffin confirmed the incident was deliberate.
"It's an attack," she said.
Ciotti said on BFM TV that police killed the driver "apparently after an exchange of gunfire." It is not known if the driver had any accomplices.
French newspaper Nice-Matin showed the truck riddled with bullet holes.
The Paris prosecutor's office has opened a terrorism investigation into the attack.
CBS2's Valerie Castro reported French officials found a cache of firearms and grenades inside the truck.
The White House condemned the tragic attack in a statement.
"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," President Barack Obama said.
Obama added that the U.S. administration is in touch with French officials and ready to offer any assistance in the investigation.
France's ambassador to the United States, Gerard Araud, characterized the events as a "terrorist attack."
Wassim Bouhlel, a Nice native who spoke to the AP near Nice's Promenade du Paillon, said that he saw a truck drive into the crowd and then witnessed the man emerge with a gun and start shooting.
"There was carnage on the road," Bouhlel said. "Bodies everywhere."
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.
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.''
Allemand said people took shelter in a nearby restaurant, where he continued to hear people shouting for missing family members. He ventured out and saw bodies, blood and body parts all along the road.
"This evening, it was horror,'' Allemand concluded.
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.
Hours after the attack, bodies covered in tabled cloths could still be seen in the street as family members embraced each other and kept vigil by their loved ones.
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. We hid in a restaurant but now we moved to a separate hotel."
Ryan Hubbs, an American visiting the resort city, said he was at a nearby restaurant when the truck sped by.
"We saw a truck come down the road at a pretty high rate of speed, probably 20, 30 miles an hour and at about that time you started to see people running, screaming, rushing away from the waterfront where everything was happening," Hubbs said.
Another witness who saw the attack from a balcony said the truck was "zig-zagging."
"I'd say it was going about 25 miles an hour as it did so and just plummeting through, looked like it was hitting several people," the witness said.
Witness Dominique Molina said it sounded like a "shooting range."
"The truck proceeded to run people over and the sounds were really horrific, you could hear banging as the truck drove over people and as soon as the truck went of out view, we could hear a barrage of gunfire and it sounded like a shooting range," Molina said.
CBS News reported that U.S. intelligence officials are gathering information on Nice.
According to the SITE Intel Group, the Islamic State for Iraq and Syria advocated for a vehicular attack in a terrorist magazine in September 2014.
"Smash his head with a rock, or slaughter him with a knife, or run him over with your car," the ISIS spokesman reportedly said.
SITE also reports pro-ISIS jihadists are "celebrating the massacre," and that "pro-ISIS groups have quickly mobilized to threaten France."
Presumptive Republican presidential nominee Donald Trump called it "another horrific attack."
"Another horrific attack, this time in Nice, France. Many dead and injured. When will we learn? It is only getting worse," Trump tweeted.
"In light of the horrible attack in Nice, France, I have postponed tomorrow's news conference concerning my Vice Presidential announcement," the billionaire tweeted.
In an interview with Fox News, Trump said he would ask for a declaration of war against ISIS as president.
"This is war," Trump said.
Presumptive Democratic presidential nominee Hillary Clinton told CNN that "we are at war" with radical jihadists.
"Radical Jihadists who use Islam to recruit and radicalize others in order to pursue their evil agenda," Clinton said.
No one has claimed responsibility for this attack.
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