As many as 84 people have been killed and dozens more critically injured after a lorry struck a crowd celebrating Bastille Day in Nice, in south-east France.

A truck drove into a crowd of people on the famous Promenade des Anglais as they watched a fireworks display, in what police have described as an “attack”.

The motive for the attack remains unknown, but anti-terrorist investigators have taken over the investigation.

The truck drove along the pavement for up to 2km, swerving to hit a maximum number of civilians.

It is unclear whether there were any other occupants in the truck, but police shot and killed the driver and are reported to have found a cache of guns and grenades in the vehicle.

One eyewitness told France’s BFMTV:

“Everyone was calling run, run, run there’s an attack run, run, run. We heard some shots. We thought they were fireworks because it’s the 14th of July.

“There was great panic. We were running too because we didn’t want to stick around and we went into a hotel to get to safety”

Police have urged people to “keep calm ” and to “not leave home”.

No group has yet claimed responsibility for the attack, but the SITE Intel Group, which monitors jihadist groups, said that “a vehicular attack such as that in Nice was advocated by ISIS spokesman ‘Adnani in September 2014 and Al-Qaeda in the Arabian Peninsula in Issue 2 of Inspire Magazine”.

The UK Foreign Office have said that they are “in touch with the local authorities following the concerning incident in Nice and stand ready to help any British nationals”.

To contact the crisis centre at the Quai d’Orsay, please call 01 43 17 56 46.