Terrified witnesses in Nice have spoken about seeing dead bodies "all over the place", as they fled the scene and hid in local businesses and homes.
Sophie Sanderlands, an Australian on holiday in Nice, told Australian breakfast show Sunrise that she had been on the beach enjoying the fireworks shortly before the attack happened.
"There was live music, people everywhere, it was a really happy mood," she told Sunrise.
"All of a sudden thousands of people just started running towards us screaming, crying, absolutely out of control."
She said she had no choice but to run with them.
As they ran towards Place Massena, she saw strollers on the ground and people desperately trying to get inside packed restaurants.
Lucy Nesbitt-Comaskey was in a restaurant in Nice and said the attack "ruined my shopping trip".
"Just before the attack there was this horrendous wind, all the tables in the restaurant, all the glasses were flying off the tables. I thought maybe there was some sort of tornado and that's when people were running and screaming down the street.
"Everyone came into our restaurant. The owners closed the doors and said to everyone please don't go anywhere.
"I thought, this doesn't sound like fireworks, it sounds like Beirut."
John Irish from Reuters Paris is seeking news about fellow journalist Matthias Galante.
"We have no news from our colleague Matthias Galante. Please retweet to help us find him."
Katja Karhia, said on Twitter she was unsure whether McDonald's was a good place to hide but was too afraid to leave.
"Good place to hide, #McDonalds? Maybe not, too afraid to go.
"They told us to go upstairs #McDonalds, doors locked. Heard somebody shooting fireworks to people."
An Iranian journalist holidaying in Nice told the Guardian she saw the truck run over people as they walked in the pedestrian area after fireworks had finished, and described seeing "dead bodies all over the place".
"Everyone was completely shocked, I saw that suddenly people were fleeing and shouting," Maryam Violet said.
"People were shouting 'It's a terrorist attack, it's a terrorist attack', it was clear that the driver was doing it deliberately.
"I was walking for nearly a mile and there were dead bodies over the place. I think over 30 dead bodies are on the ground and lots of people are injured."
One thankful teenager, Olley, said on Twitter he had never been so scared in his life and thanked God he told his mum he didn't want to go to out to watch the fireworks.
Dominique Molina tweeted: "I'm in Nice and cannot describe the situation - scary awful. Dead bodies everywhere people killed in front of my eyes. Had to be planned,"
"The sounds were horrible, moving truck driving full speed and running over people.
"To understand the horror you have to know what happened just before. Thousands on the beach watching fireworks, just after [the] show ended people disbursed (sic)."
Another man said the truck that hit the crowds had bullet holes in it.
"Enough doesn't exist anymore," Rudy Hinojosa commented.
Tony Molina told CNN that he watched the chaos from his hotel room on the promenade.
"There was still a crowd of people and then you just see this big white panel truck, I couldn't see the driver, but it just kept going at different angles from left to right at 25 to 30 miles [40-50km] an hour," he said.
"People were screaming and running. There are still people I am looking at right now that are near their deceased family members.
"I work in homicide and I've never seen anything like this. It's unbelievable."
Wassim Bouhlel, a Nice native who spoke to the Associated Press near the city's Promenade du Paillon, said: "There was carnage on the road. Bodies everywhere."
The Agence France-Presse (AFP) has said its reporter described seeing a white van driving at high speed on to the Promenade des Anglais, which is by the beach in Nice, as people were leaving after the Bastille day celebration display.
"We saw people hit and bits of debris flying around," the reporter said, adding that the attack took place near the Hotel Negresco. Terrified pedestrians screamed as they fled the area.
"It was absolute chaos."
Nice-Matin journalist Damien German said the area was dense with people when the attack occurred.
After the celebrations ended, everyone left the area at the same time - on the stairs people were "squashed like sardines".
German reported hearing a noise but thinking it was fireworks.
"But a split second later, a huge white truck travelled past at breakneck speed driving over people," he wrote.
"I saw bodies flying like bowling pins in its path. Heard noises, screams that I will never forget.
"Around me, there was panic. People were running, screaming, crying."
On the road, he saw lifeless bodies, blood, and heard groans.
CNN presenter Jim Sciutto spoke to several witnesses.
"He told me that the truck driver was mowing bodies over and accelerating as he was hitting these people on the streets.
"These streets were blocked off, no vehicles were meant to be there. These were pedestrian avenues at the peak of the fireworks.
"Witnesses say this driver intentionally broke through those cordons and then intentionally accelerated as he drove through the crowds."
• Nice's central hospital has released a number for families of the victims: 04 93 72 22 22