The death toll from flash floods in southwest France has nearly doubled to 13.

Interior Ministry spokesman Frederic de Lanouvelle said one other person is missing and five others are seriously hurt after flash floods tore through towns, turning streams into raging torrents.

He said nine of the 13 dead were clustered in one town, Trebes, in the Aude region.

France Floods
Residents watch the waters after flash floods in the town of Villegailhenc (Fred Lancelot/AP)

The official said the death toll could still rise further.

Some people had to be helicoptered to safety from the roofs of their homes as overnight storms dumped several months of rain in just a few hours.

Waters swept through roads and streams became raging torrents as the equivalent of several months of rain fell overnight in the space of hours.