French police made two more arrests on Sunday, bringing the total number of people being interrogated over Mohamed Lahouaiej-Bouhlel, who French Prime Minister Manuel Valls said was "radicalised very quickly", to seven. Lahouaiej-Bouhlel turned a refrigerated truck into a mass killing machine, ploughing through Bastille Day festivities on the crowded seafront Promenade des Anglais.

A total of 84 people, including ten children and teenagers, were killed. Another 202 were wounded.

Adelaide couple Richard and Trudy Weber were staying at the Hyatt Regency hotel on the promenade with their 15-year-old daughter (who did not wish to be named) where the truck was eventually halted when police shot  the driver dead.

The Webers told Fairfax Media they were considering joining the crowd but their daughter's need to use the bathroom saved their lives.

As they turned back for the hotel, Richard - a South Australian detective sergeant - looked up and saw the white truck hurtling down the packed strip.

"I look up and just see this truck smashing through the crowd and he was really going quite fast ... it was doing 50 [km/h] at least ... you could see the driver," he said.

"People were just screaming, there was panic and there was a crowd running into the hotel."

"I thought it was going to be a bomb," Mr Weber said. "I knew this was no car accident."

"I've seen some pretty bad things ... but nothing like this," he said.

The trio ran for the lifts of their hotel along with dozens of other people trying to escape the carnage.  "It was a stampede."

"There were dead bodies everywhere," Mr Weber said.

Trudy Weber said the experience was extremely distressing for the whole family, and the floral tributes and makeshift memorials, some positioned exactly where some of the victims last stood, compounded that distress.

"I think traumatised is saying it lightly," she said.

"On Friday we were all numb ... every time we went out of the hotel the truck was there and we saw them dusting it for fingerprints and it was a big reminder."

Ten children were among the dead, which Ms Weber said was especially upsetting for her daughter. "The memorials and the flowers were just too much for us to bear."

There has been criticism of French police given the vehicle travelled two kilometres before it was stopped however Mr Weber defended the authorities.

"It's easy to criticise ... they did shoot at him right at the beginning," he said.

The Webers cut short their stay in Nice - and travelling to another part of the south of France - after they unsuccessfully tried to get flights home. But Mr Weber said: "We'll come back to France someday."  

Australians hid in underground basement

Joelle Fuchs hid a group of people in his restaurant basement during the Nice attacks. Photo: Latika Bourke

Seven blocks back from the Hyatt Regency hotel on the promenade, Joelle Fuchs, the Belgian owner of La Fritkot, a small restaurant on Avenue Georges Clemenceau, told Fairfax Media he offered protection to Australian tourists in his underground basement until the all-clear was given.

When news spread that something major was happening on the seafront, Mr Fuchs opened up his underground basement, which he normally uses to store stock and beer.

"We thought people in the street were shooting," he said. Several police officers happened to be dining in his restaurant and quickly sought information from their headquarters.

"I said: 'Wait there and don't move because we don't know what's happening'."

The group of Australian, Canadian, Swedish and French diners remained underground for about 20 minutes, Mr Fuchs said.

Asked if he was worried that the terrorist attack would damage his take for the rest of the holiday season, Mr Fuchs said money did not matter.

"I don't care about the season ... we're OK," he said.

with Reuters

Follow Latika Bourke on Facebook