The bullet-riddle truck used in the Nice attack | Photo credit: Press Association
The speeding truck hit crowds gathered to celebrate Bastille Day. 84 people are so far confirmed dead including many children. The driver, which unconfirmed reports identified as being of Franco-Tunisian descent - was killed by French Police after an exchange of gunfire.
Dozens more people are injured and many are in a critical condition.
Eyewitnesses say bodies were flying like bowling pins as the truck careered 2km through packed crowd that had gathered to watch the annual July 14 firework display.
Francois Hollande extended France's state of emergency - which was put in place eight months ago following a series of terrorist attacks in Paris that left 130 dead - by three months
The French president addressed the nation saying the attack had all the elements of a terrorist attack. "Once again Horror has struck France" said Hollande.
“France is horrified by what has happened, this monstrosity which is using a truck to deliberately kill dozens of people who simply came to celebrate July 14. France was struck on its national day, a symbol of freedom,” said Hollande.
Hollande warned that the attack would have repercussions at home and abroad. “Nothing will make us yield in our will to fight terrorism. We will further strengthen our actions in Iraq and in Syria. We will continue striking those who attack us on our own soil”
Hollande will travel to Nice today (Friday) "to support the city and its elected members in this hardship".
US Secretary of State John Kerry sent out this message: "Today's horrendous attack in Nice is an attack against innocent people on a day that celebrates Liberty, Equality, and Fraternity. On behalf of all Americans, and especially the great many with close ties to France, I offer our deepest condolences to the friends and family of those who were killed and our hopes for a speedy recovery to those who were injured."
US presidential candidate Hillary Clinton tweeted: "Every American stands in strong solidarity with the people of France".
Meanwhile Donald Trump said he would postpone the announcement of his vice presidential running mate, due to the "horrible attack".
The White House released a statement Thursday evening condemning "what appears to be a horrific terrorist attack in Nice, France. 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," the statement from Obama read.
European Commission president Jean-Claude Juncker said: "France can count on the European Commission and EU countries for continued support in the fight against terrorism both inside and outside the European Union. Our determination will be as strong as our unity".
European Council President Donald Tusk said: "Europe stands united with the French people and government in the fight against violence and hatred".
European Parliament President Martin Schulz said: "Those who have committed this act of appalling cowardice chose a symbolic date, a moment which is special for French people and their national heritage."
"Physical and psychological wounds will be slow to heal but I call on the French people to stand strong and united against these acts of hatred. France should not surrender its values of freedom, equality, and fraternity."
Belgian Foreign Minister Didier Reynders described the attack as "barbaric."
A spokesman for New British Prime Minister Theresa May said: “We are shocked and concerned by the scenes there. Our thoughts are with all those affected by this terrible incident on what was a day of national celebration.”
New UK Foreign Secretary Boris Johnson sent a message saying he was, “Shocked and saddened by the appalling events in Nice, and the terrible loss of life.”