Police officers are still patrolling and carrying out checks in the city.

Image source, AFP

Canadian eyewitness Ramiro Mora was at the celebrations. 

He told CBC News, external: "This was a family event, there were babies, there were children, and just watching these people dragging their children down the street was unbelievable, and we're running with them."

French news agency AFP is reporting that a concert scheduled for Friday by artist Rihanna and a long-running Nice jazz festival due to take place 16-20 July have been cancelled. 

"France is in tears, grieving, but it is strong and will always be stronger than the fanatics who wanted to attack it today."

Here is a summary of Mr Hollande's defiant speech moments ago:

• He called Nice a "terror attack" and said 77 people had died, including children.
• He said he would extend the state of emergency, due to expire in late July, by three more months.
• The operation in which 10,000 extra military personnel are supporting non-military security forces, will be extended in time and scale. Many will be sent to France's borders.

• He said he would hold a meeting with security chiefs and then travel to Nice himself.
• Extremists hate human rights, he said, which is why they attacked France when it was celebrating its core values.

In his news briefing, Mr Hollande said children were among those killed in Nice. 

France "will reinforce operations in Syria and Iraq" says President Hollande.

Mr Hollande will travel to Nice shortly "to support the city and its representatives at this time of need".

"France is badly hit by this tragedy. We are horrified," he says. 

"But France is strong, and France will always be stronger I assure you.

Mr Hollande says it cannot be denied that Nice was a terror attack.

"The state of emergency, which was to end of 26 July, will be extended by three months. A law will be submitted to parliament next week for this." 

French President Francois Hollande announces the boosting of security forces numbers, both within France and at its borders.

Mr Hollande says "it is all of France which is under the threat of Islamic terrorism. So in these circumstances we must show absolute vigilance and a determination without end."

The French president says 77 people have been killed in what he said was a terror attack.

French President Francois Hollande says he deplores this attack.

"It's clear we need to do everything we can to fight against terrorism."

President Hollande is speaking now.

We now have a gallery of some images from Nice, showing emergency workers on the scene and injured people being cared for.

As ever, we are not showing some of the more distressing photos which have been circulating. 

Image source, AFP

A journalist at the local newspaper Nice-Matin has tweeted an image of its front page.

Instagram user Grace Ann posted this video on Instagram of what she called "insane Panic" as people ran from the scene.

The presumed US Democratic presidential nominee Hillary Clinton has said the attack left her sick at heart".

She told CNN it "reminds us very vividly and tragically that we need to stand with our allies and not abandon them, and we need to strengthen our alliances, including with Nato, not undermine them.

French news agency AFP has tweeted this: 

Back in January last year, France was shocked by one of its worst security crises in decades, as gunmen brought three days of bloodshed to Paris.

It began with a massacre at the offices of satirical magazine Charlie Hebdo on 7 January and ended with a huge police operation and two sieges two days later.