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Mr Hollande made the chilling warning after visiting vctims in hospital in Nice less than 24 hours after Mohamed Lahouaiej Bouhlel ploughed a rented truck into crowds of people celebrating Bastille Day. Hundreds of men, women and children were mown down leaving 84 dead and hundreds more injured. Now the French president has warned that the number of dead could rise. He said: "About 50 people are in an absolute urgency between life and death." He dded that there were a lot of foreigners and children among the dead and warned that the fight against extremist groups would be long because they would continue to try to strike at Western values. French police said Bouhlel, a 31-year-old born in Tunisia who had taken French nationality, was behind the wheel of the truck which struck on Thursday night at ariund 10.30pm. Horrific photographs posted on social media, too graphic to publish, show men and women lying dead in the road covered by blankets after a jubilant scene turned into a nightmare as France celebrated its biggest public holiday. Crowds, at some places five people deep, had packed out Nice's Promenade des Anglais to watch a glittering fireworks display when the lorry struck. The white HGV sped down the road and rammed into the crowd where it was thickest at about 40mph. Bouhlel travelled along the kerb for 100 metres, reportedly dodging police gunfire. He then burst out of the vehicle and began spraying the crowd with bullets. Images then emerged of the cab riddled with bullets. He has since been shot dead. And Foreign Secretary Boris Johnson said there was at least one Briton among the casualties caught up in the terror attack while London Mayor Sadiq Khan said safety measures in the UK capital would now also be reiviewed. One witness reported horrific scenes with "dead bodies everywhere" and distressing video footage emerged of people fleeing the Promenade des Anglais, in the southern French city, in terror. Another said it ran down terrified pedestrians "like ninepins". Fabien Lallemand said he saw a “huge white truck traveling at breakneck speed” which clearly intended to “mow down the maximum number of people”. He said: ”I saw bodies flying like bowling pins in its path. I heard noises, screams, that I will never forget. I was paralysed. I did not move.

“Around me, there was panic, people were running, screaming, crying. Then I realised. And I ran with them.” A group of students were on the Promenade des Anglais at the time of the incident. One of them, Anthony, said: “The fireworks ended, and we went back. “At that time we saw the white truck. A six tonne truck. It was speeding at 60 km/h, 70km/h. "I saw behind the wheel, the driver was deciding which way it was heading. The truck rolled on to the pavement. “It happened two meters from us. I saw people lying on the ground, I saw a small child hit the earth.” Eric Dratell, an American lawyer who is based in London, is in Nice on holiday with his wife. They were among those lucky to survive last night’s attack and were just metres away from the gunfire. Mr Dratell told Express.co.uk: “You go from, it was terrific, a lot of fun, the fireworks were spectacular, dinner was wonderful, to absolute terror in the blink of an eye. "We were on on the beach, the promenade runs about three metres above the beach. “I’ve not been watching the news reports, its just all too fresh, when we walked out last night finally after about three hours of sheltering there were bodies and blood everywhere.” Asked if it was like the scene from a horror film, he replied: "Yeah, just the people jumping off the promenade down onto the beach my wife said it was like a zombie attack, with people literally just flinging themselves.”

Bastille Day Massacre: 84 dead Sat, July 16, 2016 84 people have been killed and 100 more injured in the southern French city of Nice after a lorry was 'deliberately driven' into a crowd celebrating Bastille Day in a confirmed terrorist attack. Play slideshow REUTERS 1 of 25 French President Francois Hollande giving a statement following the attack in Nice, during a national television address in Paris

Twitter A local hospital, the Negresco, has been turned into a field hospital

British tourist Lucy Nesbitt-Comiskey described the moment police shot at the truck and people fled into the restaurant she was dining at with her friend in panic. The pair had been due to go to the fireworks display themselves but decided not to at the last minute because she needed to go to the toilet. She said: "It sounded like an attack in Beirut. I said to my friend this doesn’t sound like fireworks. All of a sudden people were screaming in the streets and they were running to the restaurants. "There was a lady, she collapsed on the floor she fainted and we were in shock. We were going to go down to the fireworks but we didn’t go because I needed to go to the ladies and that’s what stopped us. It was shocking, it was devastating." Lawyer Harjit Sarang, from London, and her children were among those caught up in the terror. She tweeted: "Running through crowds in Nice with kids and terrified. Never taking kids to a public event again. Finally back to hotel. Hate this! "Scariest thing ever running through crowds with boys. Got back to hotel and couldn't get in for people seeking refuge! "Can't stop shaking. Hate that my boys had to experience this. Why did I take them. Why did they do this and why is this happening!"

TWITTER There are unconfirmed reports the incident was a deliberate 'attack'

Twitter Police are investigating what is believed to be a possible terror attack

RT A lorry has ploughed into a crowd of people in Nice

French officials have confirmed they are investigating the atrocity as a terror attack. Bouhlel is understood to be a resident of Nice after an identity card was found at the scene. It is believed that he was a delivery driver and had rented the lorry from the Provence-Alpes-Côte d'Azur area. Two days before the attack, Bouhlel is understood to have parked on the street for nine hours and when quizzed by police, told them he was delivering ice cream. French police confirmed the terrorist was known to authorities in relation to common crimes, but not to the intelligence services. French TV channel iTele reported a gunman, believed to be the terrorists had "holed up in a nice restaurant downtown" but was then "neutralized" by police. The channel says it is not believed the man had taken any hostages during the incident. French newspaper Le Figaro quoted police sources saying officers found weapons, guns and grenades inside the lorry cab, indicating it was a premeditated terrorist attack. Police are now actively seeking out any accomplices involved in planning the atrocity and specialist anti-terror detectives from Paris have taken over the investigation from local officers.

REUTERS Pictures have emerged of bodies strewn across the road

Twitter Eyewitnesses reported scores are dead

Twitter ISIS supporters are celebrating the attack

Nobody has yet claimed responsibility for the attack but supporters of the Islamic State (ISIS) terror group have been celebrating the massacre on social media. And the Paris prosecutor's office confirmed it has opened an investigation into charges of "murder and attempted murder by an organised group linked to a terrorist enterprise". France has announced July 17 and 18 will be national days of mourning to "pay hommage" to the victims and all flags on public buildings will be flown at half mast. It is the 10th terrorist attack carried out in France since January last year. ISIS channels online have reportedly told their supporters to "await" confirmation it was behind the atrocity through an announcement by its press agency Amaq. The French Council of the Muslim Faith condemned the attack, which it called "heinous and abject", and offered its prayers for the friends and families of those killed and wounded. The Foreign and Commonwealth Office released a statement saying: "We are deeply concerned about reports of an incident in Nice and are in touch with the local authorities to seek more information. Our thoughts are with those affected and we stand by to help any British nationals." Of those injured, 18 are critical and 31 more in a serious condition. More than 100 are wounded.

EXPRESS•BING MAPS A map of Nice showing the location of the attack

There are so many casualties a local hotel - The Negresco - has been converted into a temporary field hospital. Hospitals are also appealing for blood donations fearing they could run out of supplies. The Mayor of Nice, Christian Estrosi, said on Twitter: "This is the worst drama in the history of Nice with more than 70 victims already". He urged people to stay indoors. Mr Estrosi said the truck was drivien by someone who appeared to have "completely premeditated behavior" and confirmed that "the truck was loaded with arms, loaded with grenades".

Nice Matin The truck was riddled with bullets during the incident

AFP The driver of the vehicle is said to have been killed

AFP France has been targeted by a number of terror plots

Interior Ministry spokesman Pierre-Henry Brandet confirmed the driver had been “neutralised” and added: "The investigation will determine whether he acted alone.” More than 100 people had to be rescued from the sea by local authorities after dashing into the water in a blind panic. The dead include ten children while at least 54 other youngsters were also injured. Authorities in Nice have officially enacted the ‘White Plan’, which ushers in contingency measures to deal with the aftermath of a massive terrorist attack. Hospitals have been put on red alert to receive mass casualties and armed troops have taken to the streets in huge numbers.

Twitter Police apparently fired at the lorry as it mounted the curb

Nice Matin Officials have confirmed it as a terror attack

Nice Matin More than 100 have been injured

REUTERS Police forensics experts found guns and grenades inside the truck

He drove over everyone, everyone is bleeding Eyewitness

French President Francois Holland has immediately flown back to the capital Paris from an official trip in Avignon and will chair a crisis meeting of ministers at the Elysee Palace, his spokesman confirmed. His interior minister, Bernard Cazeneuve, has already left Paris and is headed down to the south coast to visit the scene of the atrocity. Prime Minister Theresa May said that "brutal terrorists "must be defeated and that the UK stood "shoulder to shoulder" with France. A spokesman for US President Barack Obama said he had been “apprised” of the situation in Nice and “will be updated as appropriate”. Mr Obama released a statement saying: “I condemn in the strongest terms what appears to be a horrific terrorist attack in Nice. “We stand in solidarity and partnership with France, our oldest ally, as they respond to and recover from this attack.” Russian president Vladimir Putin has sent a telegram of condolence to his French counterpart Francois Hollande. Mr Putin also pledged to work closely with France on all anti-terrorism issues, said Kremlin spokesman Dmitry Peskov.

AFP Dozens of people are seriously wounded in hospital

Nice Matin There are unconfirmed reports of gunmen on the loose

REUTERS Armed police have now flooded the streets of the city

AFP The crowd was attending a fireworks display in Nice, with this photo taken moments before the drama

Donald Trump tweeted he has cancelled a press conference at which he was to announce his presidential running mate tomorrow "in light of the horrible attack in Nice". EU President, Jean-Claude Juncker, tweeted: "Strongly condemn heinous & cowardly terrorist attacks,resulting in unacceptable loss of lives." Sadidq Khan, Mayor of London, said: "Thoughts and prayers of millions of Londoners are with the victims of this horrific attack on Nice, their families & their friends." And French ambassador to the US Gérard Araud tweeted: “Again. Sadness. These people only wanted to enjoy the Bastille day fireworks with their family and their friends. Sadness. “Our democracies are besieged. Let's stick more than ever to our values. Liberté, Egalité, Fraternité. Vive la France, vive les Etats-Unis!” In a statement tonight the French Council of the Muslim Faith (CFCM), said: "The CFCM transmits its total solidarity with the inhabitants of Nice, expresses its deep sympathy to the families of the many victims and wish a speedy recovery to the injured. The group asked Muslims across France to pray "in memory of the victims of this barbaric attack" which it said hit "our country the same national day which celebrates the values ​​of liberty, equality and fraternity". A hashtag has been started up on Twitter - #portesouvertesnice - for shellshocked witnesses and victims of the attack looking for somewhere to spend the night.

Another horrific attack, this time in Nice, France. Many dead and injured. When will we learn? It is only getting worse. — Donald J. Trump (@realDonaldTrump) July 14, 2016

Canadians are shocked by tonight's attack in Nice. Our sympathy is with the victims, and our solidarity with the French people. — Justin Trudeau (@JustinTrudeau) July 14, 2016

Sickened by news of another senseless attack. On this #BastilleDay we are all patriots of France. Nice, we are with you. — Bill de Blasio (@BilldeBlasio) July 14, 2016

Just heard the terrible news from Nice. I am shocked. My thoughts and prayers to all affected. — Simon Cowell (@SimonCowell) July 14, 2016

Thoughts and prayers of millions of Londoners are with the victims of this horrific attack on #Nice, their families & their friends. — Sadiq Khan (@SadiqKhan) July 15, 2016

Among those confirmed dead is 54-year-old Linda Casanova from Agno Ticino, an Italian-speaking region in Switzerland, who is understood to have been run over by the lorry. There will be fears tonight that France has been targeted by yet another horrific terrorist attack, coming after last November's slaughter in Paris by Islamic State (ISIS) gunmen. France is still in a State of Emergency following those attacks, when almost 150 people were murdered by Islamic State and Al-Qaeda operatives. ISIS is well known for using vehicles in terrorist attacks, often packing them with explosives for maximum effect. Bastille Day, which celebrates the storming of the Bastille prison in Paris during the French Revolution of 1789, is the country's biggest public holiday.

GETTY A forensic expert examines bodies

GETTY French Prime Minister Manuel Valls