Investigations continue into Nice lorry attack as Queen pays respects to victims
French detectives are tonight trying to piece together the circumstances that left at least 84 people dead and scores injured after a terrorist deliberately drove a lorry into Bastille Day revellers, before being fatally wounded in a stand-off with armed police.
The country's president Francois Hollande said some 50 people were "between life and death", while several people are among the missing and a "small number" of Britons are injured.
Prime Minister Theresa May said Britain must redouble its efforts to defeat "brutal" terrorist "murderers", while police forces across England and Wales have been told to review security at major events over the next week in the wake of the bloodbath.
The Queen paid her own respects to the dead and injured on Friday night, sending a message to Mr Hollande saying: "I was deeply shocked and saddened to hear of the terrible loss of life in Nice.
"Prince Philip and I would like to offer our most sincere condolences to you, the families of those who have died, and the French people. ELIZABETH R."
France has declared three days of national mourning following the atrocity, which comes after attacks in November in Paris in which 130 died and in January 2015 that killed 17.
A vigil was also taking place at Nice Cathedral on Friday night.
Mr Hollande said: "France has been hit by a tragedy once again. This monstrosity of using a lorry to deliberately kill people, many people, who only came out to celebrate their national day.
"France is in tears. It is hurting but it is strong, and she will be strong, always stronger than the fanatics who wish to hurt us."
Eyewitnesses said the Nice attacker - reported to be 31-year-old Mohamed Lahouaiej Bouhlel, a man of French-Tunisian origin not known to intelligence services - swerved from side to side to kill as many people as possible as he drove for a mile along the Promenade des Anglais on the seafront of the city on the French Riviera.
He is said to have pulled a gun from the cab as part of the premeditated attack before being shot dead by police, with people fleeing into the sea in a bid to escape.
French authorities tonight confirmed 202 people were wounded, 25 of whom are on life support, while 52 are in a critical condition.
Revellers in the resort initially thought the commotion was part of a celebratory firework display, but then saw the lorry and assumed the driver had lost control.
Irish barman Robert Greene, from Coolock in Dublin, was around three metres from the bloody carnage and spoke of the devastation.
Clearly shaken by the incident, he told the Press Association: "I saw this truck and he cut through three or four people, he was already missing the bumper. It was horrific.
"A woman dropped to her knees, someone in her family had been killed, just lying there. There was not even a thing anyone could do, there was no CPR, bits of him were lying around.
"It was horrific."
The barman added: "There was a young child's plastic tricycle, smashed up and left in bits.
"I stayed on top of the stairs looking around. It was surreal. People screaming, children crying, young children running around the place alone, a woman on rollerblades screaming for her child."
Damien Allemand, a journalist with the Nice-Matin newspaper, said: "I saw bodies flying like bowling pins in its path. Heard noises, screams that I will never forget."
One tearful British holidaymaker, arriving back at Gatwick airport from Nice, said: "At first I thought it was just a road traffic accident.
"I didn't think terrorism. But when I saw the damage I thought, you can't have missed this many people. He would've used his brakes but there was no screech."
London resident Tereza Cerevenova, on holiday with her family in Nice, said people were "hiding behind cars" in an effort to escape the lorry driver.
World leaders have condemned the atrocity.
Speaking ahead of a visit to Scotland, Mrs May said the UK "stands shoulder-to-shoulder with France today as we have done so often in the past".
She said: "If, as we fear, this was a terrorist attack, then we must redouble our efforts to defeat these brutal murderers who want to destroy our way of life.
"We must work with France and our partners around the world to stand up for our values and for our freedom."
Foreign Secretary Boris Johnson, who had celebrated Bastille Day with dinner at the French Embassy in London, described the attack as "appalling and cowardly".
He said: "No country is immune to terrorism and we are united with our French and European partners as we deal with these threats to our countries and our way of life.
"British Embassy staff are on the ground in Nice and in close touch with French authorities."
Police forces in Britain will review security at major events scheduled to take place over the next week in the wake of the attack.
The Association of British Travel Agents (Abta) issued a statement encouraging people to check with their tour operators before heading to France.
There were concerns for a Scottish couple reported missing in the wake of the attacks, but they made contact with relatives later on Friday.
The Foreign Office c onfirmed that the attack was a "terrorist attack" causing multiple casualties and updated its advice for Britons in Nice.
The new advice said: "If you're in the area, follow the instructions of the French authorities, who have cancelled a number of public events planned for the coming days, closed the Promenade des Anglais and a number of the public beaches in and around Nice, and implemented some traffic restrictions."