UPDATED Monday, October 5 18:37: Storm Alex struck swiftly and violently on Friday, causing flash floods that took a heavy toll along the Cote d’Azur as an unusual red alert came into force.

A total of 20 people were unaccounted for on Monday morning and the number of bodies retrieved rose to four.

President Emmanuel Macron will visit the region on Wednesday.

In some locations the downpours reached five centimetres within a 24-hour period.

The regional train service came to a halt at midday on Friday and Nice Airport ceased operating by 21:00 on Friday.

In Monaco, the Government made several hundred beds available at the local convention centre for commuters who could not return to their own communities, although this was not called into use.

On Saturday, 850 firefighters were employed along the Cote d’Azur to help locate missing persons and to check on damage to homes and infrastructure.