Eyewitnesses reveal the chaos and carnage of Nice terror attack.

An Australian journalist caught up in the deadly Bastille Day attack in Nice, France, has captured incredible footage of terrified people huddling together in a restaurant store room as chaos reins outside.

The video was posted to Twitter by UTV Ireland producer Ben Terry, who took shelter in the restaurant after hearing gunshots near the Promenade des Anglais.

Crammed into the crowded space, Terry began filming on his mobile phone. The shaky footage shows two women crouched on the floor clinging to each other, fearful expressions on their faces. Someone calls for the door to be closed, while others plead with the group to stay quiet.

At least 80 are dead and more than 20 critical, with dozens more injured after a truck travelling 60-70km per hour plowed into crowds gathered to watch Bastille Day fireworks, before the driver climbed out and opened fire on those nearby.

“It was a scene of mass panic like I haven’t really seen before,” Terry told UTV.

“We were actually enjoying the fireworks display on Promenade des Anglais and we just turned off the street and two seconds later we saw people running towards us.

“We heard several gunshots, of course we had no idea where they were coming from, but after the Paris attack and we what saw in Brussels recently there was a sense of tension and we ran with the crowd.”

Image: Ben Terry.

He continued: “We managed to run up the side ally into a resultant and we quickly ran into a store room there and were huddled up with a bunch of other people. Several of them were crying, some were trying to call their family and more and more people were running in.

“A few of them looked to be injured, possibly just injuries they received while trying to get away from scene, but the sense of panic was everywhere.”

Meanwhile, other personal accounts are emerging via social media as authorities work to make sense of the chaos and carnage that unfolded in the city overnight.

A French-born editor at The Guardian US shared her family's heartbreaking experience on Twitter, saying "I have family in Nice and when they tried to go home in the chaos the kid apparently said 'Mommy let's not take the bus in case it explodes'."

"So this is what terror does to children. Heartbreaking," she continued.

A London-based lawyer described on Twitter being left "terrified" and "shaking" after being forced to flee the scene with her boys.

"Running through crowds in Nice with kids and terrified," Harjit Sarang, 42, tweeted. "Never taking kids to a public event again. Finally back to hotel. Hate this."

British woman Esther Serwah told The Telegraph UK the horror of seeing people scramble over the bodies of people killed and injured.

"I was just walking to the Promenade and then I saw everybody running and I just didn't know what was going on. People were screaming at me in French but I didn't understand.

"Some people were lying on the streets dead and people were running over the bodies. Everybody was saying it's a terrorist attack. It's just horrible, horrible, horrible. I'm in shock. I'm still shaking."

A number of Australians were present during the attacks, reporting to local media about what they saw unfold.

Among them, ABC News 24 producer David Coady who described the promenade being packed with families celebrating and watching fireworks.

"I looked towards a truck and I thought it was out of place, was among the crowd, and then I started hearing screaming and so I turned and started to run with the crowd away from the screaming," he said according to ABC.

"There was a lot of panic at the time, I was running past restaurants where people had got up and left their meals.

"People were trying to get into hotels, any businesses that were open, trying to take shelter because it was unclear what was happening and with each bang that we heard behind us, people perhaps started to go a bit faster, people were tripping over, it was a very chaotic scene.

"Of course France is very tense at the time, still in the state of emergency after last year's terror attacks in Paris. There's a lot of security around but on the promenade itself there wasn't any particular cordon."