Nice terrorist attack: This is what we know so far.

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At least 84 people are dead, including 10 children, and up to 202 others are believed to be injured following a terrorist attack in the southern city of Nice, France.

As many as 52 people are fighting for life with critical injuries in hospital. 

The attack occurred just after 11pm local time (7:48am AEST) on 14 July, when a lorry accelerated into crowds of tens of thousands during a Bastille Day celebration along the popular beachside Promenade des Anglais.

Islamic State reportedly officially claimed responsibility for the attack on Saturday.

The vehicle was travelling at around 60-70km per hour, and was reportedly loaded up with grenades and weapons.

The driver, who has been named by the Paris prosecutor as 31-year-old French Tunisian Mohamed Lahouaiej Bouhlel, was shot dead at scene.

It is understood Bouhlel lived locally and was a married father of three. He was known to police for a history of crimes including theft and violence dating back to 2010, but was unknown to counter-terror agencies.

His ex-wife has been arrested and held in custody, Paris prosecutor Francois Molins said in a press conference.

The first images of Bouhlel, apparently from his French residency visa, have been published in European media outlets.

French police have been searching the attacker’s home.

“Investigations are currently under way to establish if the individual acted alone or if he had accomplices who might have fled,” interior ministry spokesman Pierre-Henry Brander said, according to ABC News.

Police in Nice arrested three people in early morning raids on Saturday local time in trying to determine whether he had help within his entourage.

Bouhlel was said to have shouted "Allahu Akbar" – meaning "God is great" in Arabic – before being killed.

The attack comes just eight months after gunmen killed 130 people in the Paris attacks. 

Three days of mourning announced.

French President Francois Hollande gave a press conference about the attack, announcing three days of mourning for the European country.

He has also confirmed several children are among the victims of the attack.

Around 50 children are in hospital, with some clinging to life, AFP reports.

"France has been struck on the day of her national holiday... the symbol of liberty," Hollande said.

"France as a whole is under the threat of Islamic terrorism. We have to demonstrate absolute vigilance and show determination that is unfailing."

Hollande announced that the nation's state of emergency, which was due to end later this month, would now be extended.

He said authorities were working to discover if the driver of the truck had any accomplices.

In a tweet after his address Hollande reiterated the message of strength: "France is weeping, afflicted but she is stronger and will always be stronger than the fanatics who hit us today."

Three Australians were injured in the attack, Foreign Minister Julie Bishop said.

Australian tour company Top Deck has confirmed that one of its customers has suffered minor injuries.

A spokesperson for the company said, "As of 02.30 local time, all of our customers are safe and accounted for. Unfortunately one of our customers has reported some minor injuries.

"They are with Topdeck staff and are currently being tended to in hospital. Our family liaison team has been in direct contact with the injured customer’s family and we are ensuring the best care possible."

A tweet from Major Christian Estrosi shortly before the attack: 

Eyewitness accounts.

A reporter from Agence France-Presse (AFP) saw the incident occur and described the scene as "absolute chaos", according to The Guardian.

"We saw people hit and bits of debris flying around," he said, adding that the crash took place near the Hotel Negresco with many terrified pedestrians screaming as they fled the area. "It was absolute chaos."

A security cordon was quickly established around the area with a spokesperson from interior ministry confirming the driver was shot dead at the scene.

"We almost died. It was like hallucinating... (the lorry) zigzagged," another eyewitness told i-Tele.

"You had no idea where it was going. My wife... a metre away ... she was dead.

"The lorry ripped through everything. Poles, trees, we have never seen anything like it in our lives. Some people were hanging on the door trying to stop it."

World leaders respond.

Australian Governor-General Peter Cosgrove, who is in Paris for Bastille Day celebrations, released a statement on his Facebook page, saying he was "in shock".

Current and former world leaders and politicians have expressed horror and sympathy over what's occurred in Nice.

US President Barak Obama has issued a statement:

"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.

"Our thoughts and prayers are with the families and other loved ones of those killed, and we wish a full recovery for the many wounded.

"I have directed my team to be in touch with French officials, and we have offered any assistance that they may need to investigate this attack and bring those responsible to justice.

"We stand in solidarity and partnership with France, our oldest ally, as they respond to and recover from this attack.

"On this Bastille Day, we are reminded of the extraordinary resilience and democratic values that have made France an inspiration to the entire world, and we know that the character of the French Republic will endure long after this devastating and tragic loss of life," he said.

Australian Prime Minister Malcolm Turnbull said Australia and France are "united in freedom's cause".

"Only eight months ago we mourned for the victims of terrorist attacks in Paris. Now once again we mourn for the victims of another murderous act of terror in France overnight, on Bastille Day," he said.

"A few hours before, Australian and New Zealand Servicemen and women had led the Bastille Day parade in Paris. One of our great modern ANZACs, the Governor General, General Sir Peter Cosgrove AK MC represented Australia.

Turnbull continued:

"Shortly after the attack in Nice I spoke with Sir Peter as well as the Prime Minister of New Zealand John Key and our Ambassador to France, to confirm their safety and that of our embassy staff and guests.

"Sir Peter and Prime Minister Key spoke to me of their enormous pride in seeing, a hundred years on, the ANZACS of today leading the Bastille Day Parade in Paris - a recognition of the sacrifice and heroism of a century ago and also of our resolute solidarity with the people of France in the struggle against Islamist terrorism today.

"Our deepest sympathies and condolences are with the people of France. Our nations are united in freedom’s cause today, just as we were a hundred years ago."

Opposition Leader Bill Shorten said the Australian people stand with France.

"Our hearts go out to the loved ones of those who have lost their lives and our thoughts are with the injured. 

"In this new moment of sorrow, we stand in solidarity with our great friends, the French people, against this terrible violence. A crime aimed at the innocent people of France, perpetrated on their national day.

"Bastille Day has always been an occasion to celebrate the powerful belief the French people have in democracy - the struggle and sacrifice with which they achieved it, and the enduring power of the words Liberté, égalité, fraternité.

"These values, infinitely stronger and richer than the hate-filled ideology of those who seek to strike against the French Republic, have stood the test of time.  They will prevail."

Justin Trudeau was among many leaders who tweeted a response:

The Guardian reports that Chinese prime minister Li Keqiang also condemned "terrorism in all forms" and offered his condolences to the victims and their families, while speaking on a visit to Mongolia.

Australian landmarks including the Victorian parliament, Adelaide town hall, Perth Council House and Brisbane City Hall have also lit up in blue, red, and white.

Meanwhile, a French flag is currently flying over Sydney harbour in solidarity.

Hundreds have gathered at Sydney's Circular Quay in an evening candlelight vigil to reflect on those injured and killed, news.com.au reports.

How newspapers in Europe are reporting the attack:

Local paper Nice Matin tweeted: "If you are looking for a place to find cover, use #PortesOuvertesNice (doors open Nice)".

The hashtag is gaining steam on social media as a way for people in Nice to find a safe place to shelter in the wake of the attack.

It's a movement that first sprung up in the wake of the Paris attacks last year, offering shelter to travellers or people blocked from their homes due to police operations in their neighbourhood.

Concerned about friends or family? Call DFAT: 1300 555 135 or +61 2 6261 3305 (if outside Australia).