If elected president, Republican candidate Donald Trump said he would ask Congress for a declaration of war on the Islamic State (IS), according to news reports.

The billionaire real estate mogul had reportedly said this during an interview with Fox News Channel’s after a truck ploughed through a crowd, leaving 80 dead in Nice, France.

“This is war,” he was quoted as saying.

Trump also promised to be extreme in terms of documentation with regard to those coming to the US.

"I would not allow people to come in from terrorist nations. I would do extreme vetting. I would call it extreme vetting, too.

“And, you know, our country has tremendous problems. We don't need any more of the problems."

"What are we doing? We're trying to be so nice and so civil. We're so weak. The world has gotten to straighten up. We have to be very tight with our borders.

“It's now a different world... This isn't 40 years ago and 80 years ago. This is a different world. We're trying to be so politically correct. And we're making such big mistakes," he said.

Following the attack, Trump tweeted: “Another horrific attack, this time in Nice, France. Many dead and injured. When will we learn? It is only getting worse.”

He has also postponed the announcement of his vice-presidential pick in view of the incident.

French media, citing a police source, reported that ID papers belonging to a French-Tunisian were found in the truck.

A source told NBC News the driver is believed to have been a French national of Tunisian descent.

Among those killed were seven children.