US president Barack Obama has condemned "in the strongest terms" what he said "appears to be a horrific terrorist attack" in Nice, France.

World leaders reacted with horror and sadness after the attack which has left at least 80 people dead.

In a statement tweeted by the White House, the president offered assistance to French officials to investigate and "bring those responsible to justice".

He said his "thoughts and prayers" were with the loved ones of those killed and wished those wounded a full recovery.

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

"On this Bastille Day, we are reminded of the extraordinary resilience and democratic values that have made France and 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."

We know that the character of the French Republic will endure long after this devastating and tragic loss of life

Maltese prime minister Joseph Muscat said the values of liberty, equality and fraternity should inspire us more than ever before.

Former French president Nicolas Sarkozy said he felt "deep emotion and infinite sadness" after the attack.

In a tweet he professed solidarity with the people of Nice and the Alpes-Maritimes department.

Presumptive US Republican presidential candidate Donald Trump was due to name his running mate on Friday morning, but said he was postponing the announcement in "in light of the horrible attack in Nice, France".

US Democratic presidential hopeful Hillary Clinton issued a statement saying it appeared that terrorists had struck one of the United States' "closest allies in Europe, attacking families celebrating the history and culture of their country on Bastille Day".

Hillary Clinton

She said that Americans stood strong with the people and added: "We will never allow terrorists to undermine the egalitarian and democratic values that underpin our very way of life.

"This cowardly attack only strengthens our commitment to our alliance and to defeating terrorism around the world.

Canadian prime minister Justin Trudeau tweeted: "Canadians are shocked by tonight's attack in Nice. Our sympathy is with the victims, and our solidarity with the French people."

The president of the Alpes-Maritime department, Eric Ciotti, said he felt "immense emotion" in the face of the "terror" which had hit the city.

Christian Estrosi, president of the Provence-Alpes-Cote d'Azur region, called the attack "the worst tragedy in the history of Nice" because of the death toll.

France's ambassador to the United States, Gerard Araud, called the events in Nice a "terrorist attack".

At a Bastille Day reception at the French embassy in Washington, he said: "Our democracies - France, the United States, our other partners, we are besieged, we face a terrible threat."

President of the European Council Donald Tusk said on Twitter that it was a "tragic paradox" that the victims of the attack in Nice were celebrating "liberty, equality and fraternity" - France's motto - on the country's national day.

Mr Tusk tweeted a photograph of himself and other European and Asian leaders standing in tribute to the Nice victims at the Asia-Europe meeting in Mongolia.

Scotland's First Minister Nicola Sturgeon wrote on Twitter: "Dreadful reports from Nice. Thoughts with all involved."

France's prime minister Manuel Valls said on Twitter that the city had been "hit by terrorism" on the national feast day and that the country was in mourning after immense pain.

US secretary of state John Kerry issued a statement in which he called the incident a "horrendous attack" against innocent people.

He said: "I was proud to stand alongside French leaders earlier today at Bastille Day celebrations in Paris, and the United States will continue to stand firmly with the French people during this time of tragedy. We will provide whatever support is needed."

The German foreign office tweeted: "A great shock! We stand firm by the side of our French friends.Our thoughts are with the victims,their relatives,with the people of France."

British ambassador to France Julian King said that the embassy crisis centre had been activated, and tweeted: "Thoughts with the victims and their families."

In a statement, Australian prime minister Malcolm Turnball said that just a few hours before the attack, servicemen and women from Australia and New Zealand had led the Bastille Day parade in Paris.

He said: "We mourn for the victims of another murderous act of terror in France overnight, on Bastille Day."

The United Nations Security Council issued a statement condemning the "barbaric and cowardly terrorist attack" and underlined "the need to bring the perpetrators of these terrorist acts to justice".