Flowers in the colors of the French flag are laid down following the terror attack in Nice | John MacDougall/AFP via Getty Images At least 84 dead after truck hits crowd in Nice President Hollande calls Bastille Day attack ‘terrorism.’

PARIS — At least 84 people were killed Thursday in the southern French city of Nice when a truck plowed through a crowd gathered for Bastille Day celebrations, in an attack that President François Hollande described as an act of "terrorism."

It was the third major attack to have hit France since early last year. Authorities said a man drove a 19-ton truck at high speed around 11 p.m. local time into a crowd of revelers who had come to watch fireworks from the Promenade des Anglais, Nice's iconic boardwalk overlooking the Mediterranean.

France's anti-terrorism prosecutor François Molins said Friday afternoon that 10 children and adolescents were among the dead. He said more than 200 people had been injured in the attack, and that 52 of those were still in critical condition.

The driver of the truck was identified by Molins as 31-year-old Mohammed Lahouaiej-Bouhlel, a delivery driver who was born in Tunisia in 1985 and had been living in Nice. Molins said Lahouaiej-Bouhlel was killed in a shootout with police after having driven two kilometers along the promenade.

The prosecutor said the suspect was known to local authorities for petty crimes, and had been given a six-month suspended sentence in March for a violent altercation after a traffic accident. But Molins added that Lahouaiej-Bouhlel was "entirely unknown" by intelligence services.

"Once again we have seen extreme violence and it is obvious that we must do everything to fight against this terrorism," Hollande said at a press conference in Paris earlier on Friday. "France has been hit on its national day, July 14, our national symbol."

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The attack prompted further tightening of security in a country already on high alert and still smarting from a major attack last November that killed 130 people in Paris. The death toll from a series of Islamist-inspired attacks — which started in 2012 with a killing spree by gunman Mohamed Merah — now exceeds 200.

In response, Hollande said that 10,000 military officers around the country would be mobilized, border security would be strengthened, and a national state of emergency, originally due to lapse on July 26, would be extended.

The president, who had been in Avignon on a private visit when the attack happened, returned quickly to Paris during the night. He convened an emergency defense council at his office early Friday to discuss a response with Prime Minister Manuel Valls, Defense Minister Jean-Yves Le Drian, Justice Minister Jean-Jacques Urvoas and the chief of armed forces, Pierre de Villiers. France is already participating in a U.S.-led coalition against the ISIL group in Syria and Iraq.

Speaking to reporters after the meeting, Valls said that Hollande had decreed three days of national mourning for France, from July 16-18.

"Times have changed," Valls said. "France has to learn to live with terrorism."

Hollande and Valls later traveled to Nice to meet with Interior Minister Bernard Cazeneuve and other authorities on the scene. Speaking after a visit to a hospital where many of the wounded were being treated, Hollande said the injured people were "between life and death" and called for “emotional solidarity” with the victims and their families.

“We are faced with a struggle that will be long because we have an enemy who is determined to strike,” Hollande said.

No international terror group had claimed responsibility for the attack by Friday afternoon. But Hollande said it was carried out "to satisfy the cruelty of an individual or possibly a group."

Mute outrage

While Hollande's announcements aimed to reassure, they also raised questions about the limits of conventional measures to thwart attacks. Nice's attack underscored how determined terrorists could carry out a devastating strike, even during a state of emergency that grants police sweeping powers to detain and question suspected terrorists.

In a country where it's now commonplace to see machine gun-toting soldiers patrolling streets, further ramping up security could shatter any impression of life-as-normal in a peaceful western democracy, while interfering with business in Europe's third-biggest economy.

Politically, the attack is likely to further polarize an already deeply divided electorate.

After a bloody year, the so-called spirit of January 11 — the day when millions of French people rallied in the name of free speech after an attack on the offices of satirical weekly Charlie Hebdo — is a distant memory. Now the country greets fresh attacks with mute outrage and a sense of grim foreboding.

If the fallout from past attacks is any guide, voters will turn to the executive branch — Hollande, Valls and Cazeneuve — for guidance and authority through a traumatic event. Hollande's polls scores, which have been dismal for years, briefly rebounded after last November's attack, only to drop back down weeks later.

But past attacks also bolstered the popularity of Marine Le Pen's far-right National Front party. In the first round of regional elections last December, held weeks after the Paris killings, the Front outperformed all mainstream parties. Only tactical voting in the runoff round stopped Le Pen from winning a prestigious post as president of France's northernmost region.

Now, all eyes are on France's 2017 presidential election. Hollande's poll scores are near record lows; the conservative establishment is caught up in a fractious primary process; and Le Pen is as high as ever in opinion surveys, her anti-EU stance bolstered by Britain's vote last month to leave the EU.

So far, the prospect of Le Pen winning the 2017 election has appeared remote. But National Front strategists, while recognizing that the presidency remains a long shot, argue that further terrorist attacks could tip the balance in her favor.

In response to the attacks, Le Pen called for a declaration of war against Islamic fundamentalism.

"The war against the plague of Islamist fundamentalism has not started, it's urgent to declare it now," the National Front leader said in a statement. "To shock and compassion we must now add action, the necessary measures of prevention and repression, and our total determination to eradicate the plague."

Fake weapons found

Molins said police found a handgun in the truck, as well as some "replica" automatic rifles and grenades. He said the only other items in the back of the refrigerated truck were a bicycle and some empty pallets.

.@PHBrandet (porte-parole) : l'individu qui conduisait le camion a été neutralisé. L'enquête déterminera s'il a agi seul #Nice — Ministère Intérieur (@Place_Beauvau) July 14, 2016

The French government earlier denied press reports that hostages had been taken during the incident.

A reporter for the AFP news agency described seeing a white van driving at high speed onto the Promenade des Anglais.

"People are running. It's panic. The truck mounted the Prom, he drove over everyone," a journalist for local newspaper Nice Martin reported.

Cher niçois, le chauffeur d'un camion semble avoir fait des dizaines de morts. Restez pour le moment à votre domicile. Plus d'infos à venir — Christian Estrosi (@cestrosi) July 14, 2016

Obama, Trudeau offer condolences; Brussels pledges unity

U.S. President Barack Obama offered condolences and said the United States will offer any investigatory resources that are needed.

“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,” Obama said in a statement. “We stand in solidarity and partnership with France, our oldest ally, as they respond to and recover from this attack.”

Canadian Prime Minister Justin Trudeau issued a statement of condolences via Twitter. "Canadians are shocked by tonight's attack in Nice. Our sympathy is with the victims, and our solidarity with the French people," he said.

European Commission President Jean-Claude Juncker said he was “very touched and saddened by the terrible ordeal,” in a statement released early Friday morning.

“I would like to express greater solidarity with the victims, their families and all French men and women today in mourning following the cowardly act of terror,” Juncker said.

“France can count on the European Commission to continue to support it and the other states of the European Union in the fight against terrorism within and outside the European Union. Our determination will remain firm, as will our unity,” Juncker added.

Officials said the attack would be discussed Monday at a previously scheduled meeting of EU foreign ministers in Brussels.

The Nice attacks come eight months after terrorists affiliated with ISIL attacked Paris nightspots November 13 and left 130 people dead, and after the Brussels terror attacks in March.

ISIL has repeatedly stated France is its prime target, and the country has been under a state of emergency ever since the November 13 Paris attacks. Hollande had announced the state of emergency would end later this month, the AFP reports.

"We have a duty to talk about it today: Our country is not armed against Islamist terrorism," said Georges Fenech, the center-right author of a parliamentary report that probed security failures during France's terrorist attacks.

This story will be continuously updated with new information as it develops.

Correction: This story has been updated to correct the spelling of the suspect's last name.

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