'Drowned in their homes'

"We must with all urgency shed light on this unacceptable and incomprehensible tragedy," he said.

"We have to ask ourselves how in France in the 21st century families can be surprised in their sleep and die, drowned in their homes."

Nazanine Moshiri, Al Jazeera's correspondent in London, said there were serious questions about building rules on the coast and the safety of sea levees.

Philippe de Villiers, a right-wing politician who heads the regional government in Vendee, told France-Info that the "sea wall that broke dated from [the era] of Napoleon".

"Either we build [new] sea walls, in which case they need to be taller and taller ... or we have to build further'' inland.

Thousands of French firefighters and emergency workers have been deployed to reach residents who have been stranded by the floods, taking boats to flooded houses.

Hundreds of families slept in shelters on Sunday night set up in schools and dance halls.

The storm hit France early Sunday with eight-metre waves, surprising residents in their beds and sending them scrambling onto rooftops. The wind reached speeds of 150 km per hour.

In Portugal's Azores islands, a flash flood swept a school bus off a road.The driver and one child are missing on Sao Miguel, one of the archipelago's nine islands.