She said she had been on her way to the Promenade des Anglais for dinner with her daughters when people started screaming at her.

Mrs Serwah, from Surrey, said: "I was just walking to the Promenade and then I saw everybody running and I just didn't know what was going on. People were screaming at me in French but I didn't understand.

"Some people were lying on the streets dead and people were running over the bodies. Everybody was saying it's a terrorist attack. It's just horrible, horrible, horrible. I'm in shock. I'm still shaking."

A Rihanna concert scheduled for Friday night at the Allianz Riviera stadium in Nice has been cancelled, as have the city's jazz festival, which was due to run from Saturday to Wednesday, and some of the Bastille celebrations over the weekend.

World leaders express shock, outrage and solidarity

Middle East states and leading Muslim clerics united Friday in condemning the truck attack, calling for a joint struggle against extremism.

Sunni Islam's leading centre of learning, Al-Azhar, said the "vile terrorist attack" contradicted Islam and urged the world to unite efforts "to defeat terrorism and rid the world of its evil".

Tunisia said that the attacker, who police said held joint French-Tunisian citizenship, had committed an act of "extreme cowardice" and expressed solidarity with France against the "scourge of terrorism".