At least 84 have lost their lives and over 200 others sustained injuries when a truck ran through a crowd of people celebrating the French National Day, commonly known as the Bastille Day, in the southern French city of Nice.

The truck rammed into the crowd on Thursday night as people had converged on the Promenade des Anglais in the city during a firework display.

Interior Ministry spokesman Pierre-Henry Brandet said Friday that 18 people are in critical condition.

Nice Mayor Christian Estrosi, who was attending the celebration at the time of the assault, tweeted, “Dear people of Nice, the driver of a truck seems to have left dozens dead. Stay for now in your home.”

Estosi described the incident as “the worst tragedy in the history of Nice.”

The local government chief further noted that weapons and grenades were found inside the truck after the driver was shot and killed.

AFP quoted a police source as identifying the driver as a 31-year-old man from Nice of Tunisian origin. "The identification of the truck driver is still underway," he said.

This photo allegedly shows the truck that plowed into the crowd.

An image published on Twitter showed a white lorry stopped in the middle of the promenade with its front badly damaged. Four police officers were also taking cover behind a palm tree.

Another picture showed a dozen people lying on the street in the aftermath of the truck attack. Social media video also showed people running through the streets in panic.

Medics tend to the victims of an attack in the southern French city of Nice on July 14, 2016.

“Everyone was calling run, run, run there's an attack run, run, run. We heard some shots. We thought they were fireworks because it's July 14,” an eyewitness told BFM television news network.

“There was great panic. We were running too because we didn't want to stick around and we went into a hotel to get to safety,” the witness added.

There were some reports of gunfire exchange between security forces and the occupants of the lorry, but they have not been confirmed.

Bodies are seen on the ground after a van plowed into a crowd in the French Riviera town of Nice, killing 80 people, July 14, 2016. ©Reuters

A spokesman for the French Interior Ministry also dismissed reports of a hostage situation in Nice.

'Terrorist attack'

Meanwhile, French President Francois Hollande, who was in the southeastern commune of Avignon, returned to Paris to join crisis meetings at the Interior Ministry.

Later in comments broadcast live on TV, the French president said the truck attack in Nice was of a "terrorist character".

"Nothing will make us yield in our will to fight terrorism. We will further strengthen our actions in Iraq and in Syria. We will continue striking those who attack us on our own soil," he said, in reference to the Daesh Takfiri group.

‘Barbaric terror assault’

In a Paris-drafted statement, the UN Security Council condemned “in the strongest term” the “barbaric and cowardly terrorist attack in Nice.

“Any acts of terrorism are criminal and unjustifiable,” said the 15-member council, describing terrorism as one of the most serious threats to global peace.

Medics are evacuating the severely wounded to hospital following the attack in Nice.

Local media outlets reported that the French anti-terrorism investigation department has been tasked with investigating the truck attack in Nice.

Even though no group has claimed responsibility for the attack, militant outfits affiliated to the Takfiri Daesh terrorist group were reportedly celebrating the deadly incident on social media networks.

The deadly attack took place just a few hours after Hollande said the country would not extend a state of emergency, which was imposed following last November’s deadly terror attacks by the Daesh Takfiri terrorist group in and around the capital Paris.

Hollande said in his comments that the state of emergency was extended by three months.