People who fear their relatives may have become caught up in the Nice terror attack are being urged to use specially-dedicated social media channels to locate their loved ones.
It comes as France was rocked by an attack which saw 84 people killed after a large truck mowed through revelers gathered for Bastille Day fireworks.
Facebook has activated a safety check feature which enables users to quickly find and connect with friends in the area.
Users can also mark themselves, as well as friends and family as safe using the feature.
Several Twitter accounts have also been set up, which are publishing pictures of relatives and friends currently missing after the attack.
The British Embassy in Paris has advised that UK citizens in the area follow the instructions of the French authorities. The embassy’s 24-hour number is +33144513100.
While no one has yet claimed responsibility for the attacks, President Francois Hollande addressed national television early on Friday morning, stating: “All of France is under the threat of Islamic terrorists.”
The truck plowed into the crowd over a distance 2km he said, and broadcast footage showed a scene of horror up and down the promenade.