A large truck plowed into a festive crowd leaving a Bastille Day fireworks display in the French Riviera city of Nice on Thursday night, killing at least 84 people and injuring more than 100 in another likely terror attack on French soil.

“It’s a scene of horror,” said French Member of Parliament Eric Ciotti, adding that the truck “mowed down several hundred people.”

The manager of Le Queenie restaurant on the Mediterranean waterfront said that “people went down like ninepins” as the truck tore through the crowd for more than a mile, leaving bodies sprawled along the thoroughfare.

Another witness, Franck Sidoli, said, “I saw people go down. Then the truck stopped, we were just 5 meters away. A woman was there, she lost her son. Her son was on the ground, bleeding.”

At least two Americans, a father and his 11-year-old son, were among those killed.

A Manhattan woman, Annie Kleinschmidt, told the Daily Mail that no one had heard from her aunt, Claire Benchimoun, who had attended the fireworks display.

One witness, an American ­pilot, told CNN that the driver sped up and deliberately steered the vehicle toward the densest part of the crowd — and kept ­accelerating as he mowed down scores of victims.

Inside the truck were documents belonging to a 31-year-old Tunisian-born man who was a resident of Nice, ­according to the Daily Mail.

Witnesses said the truck driver was shouting, “Allahu Akbar” — Arabic for “God is great” — in the moments before police shot him dead, the Mail’s website said.

Images of the carnage gave testament to the nightmare.

One heartbreaking photo showed a body covered in plastic sheeting with a child’s doll next to it.

Another witness said he saw the driver slam into the crowd, emerge from the truck with a gun and open fire.

Police rushed over, shot the killer dead and then found ­an arsenal, including grenades, in his ­vehicle.

Others described a gruesome tableau that has become all too ­familiar across Europe.

“There was carnage on the road. Bodies everywhere,” said Wassim Bouhlel, a Nice native.

Another witness said, “We saw people hit and bits of debris flying around.”

London lawyer Harjit Sarang, 42, was in Nice with her husband and her 6- and 9-year-old sons.

“The fireworks had just finished and we were walking just off the main promenade when we saw people running and screaming through the streets,” she told The Mirror.

“My eldest son was yelling at us, ‘Why have you brought me here, I’m never coming here again!’ ”

Tony Molina of San Diego was there with his wife and son to see the fireworks.

“This white panel truck was going right across the area in front of us, and it was zigzagging. I’d say it was going about 25 to 30 miles an hour as it did so and just plummeting through,” he told CNN.

A student described the horror.

“The fireworks ended and we went back. I saw, behind the wheel, the driver was deciding which way he was heading. The truck rolled onto the pavement.

“I saw people lying on the ground, I saw a small child hit the earth,” the student said.

Police and ambulances rushed to the scene and authorities from the local Alpes-Maritimes region urged residents to stay indoors.

The truck had breached an area that had been cordoned off to keep vehicles out.

Warning: Graphic images below

While no group has been identified as being behind the attack, ISIS supporters were celebrating the massacre on social media as jihadist websites posted memes mocking French President François Hollande, according to Vocativ.com.

President Obama condemned what “appears to be a horrific terrorist attack” while offering French officials “any assistance” they need to investigate the crime.

Hollande confirmed that dozens of people, “including children,” died in the attack, which came on France’s national holiday.

“France as a whole is under the threat of Islamic terrorism,” the French leader said.

“We have to demonstrate absolute vigilance and show determination that is ­unfailing.”

Hollande said he will call a Defense Council meeting Friday that brings together defense, interior and other key ministers.

While authorities have not officially labeled the incident an act of terror, Hollande flatly said, “We cannot deny that it was a terror attack,” the latest in a string of such atrocities to shake his nation.

Last November, a team of radical Islamists armed with grenades and assault weapons in Paris targeted a concert venue, a sports stadium, several bars and a restaurant, killing 130 people and wounding 350.

In January 2015, jihadis stormed the Paris office of the satirical magazine Charlie Hebdo while an Islamist gunman at a kosher market fatally shot two people and took hostages. In all, 20 people were killed and 22 wounded.

Anne Hidalgo, the mayor of Paris, tweeted Thursday, “On behalf of all Parisians, all of our fraternal support [goes] to the people of Nice. Our cities are united.”

ISIS and other Islamists urging attacks on the West have instructed followers online to use vehicles to carry out mass killings.

In response to the Nice attack, presumptive GOP presidential candidate Donald Trump, appearing on Fox News’ “The O’Reilly Factor,” said that as commander in chief, he would ask Congress for a declaration of war — but he did not say against whom.

“This is war,” Trump said. “If you look at it, this is war coming from all different parts. And frankly, it’s war and we’re dealing with people without uniforms.”

Presumptive Democratic nominee Hillary Clinton called for an “intelligence surge” to combat the increase of radicalization among jihadist groups.

With Post wire services