Flash floods tore through towns in southwest France, turning waterways into raging torrents that killed at least 10 people, authorities have said.

People had to be helicoptered from the roofs of their homes as overnight storms dumped the equivalent of several months of rain in a few hours.

Initially, the French interior ministry announced 13 deaths from the floods in the Aude region.

But French prime minister Edouard Philippe said after visiting damaged areas that the number was corrected to 10.

Authorities said some victims had been counted twice.

In the town of Villegailhenc, resident Ines Siguet said floodwaters rose so quickly after the rains swept in from the Mediterranean that residents fled to rooftops.

Ms Siguet, 17, posted video of a ripped-up road where a bridge used to stand.

France Floods
An overturned car is pictured in front of a church in the town of Villegailhenc (Fred Lancelot/AP)

“There’s nothing left. There’s just a hole,” the teenager, whose school was closed amid the destruction, said.

“It was very violent.”

Residents described violent walls of water that crashed through doors and quickly inundated homes.

Some of the dead appeared to have been swept away by floodwaters, Aude prefect Alain Thirion said.

France Floods
People try to pull a car out of a torrent (Fred Lancelot/AP)

In the town of Conques-sur-Orbiel, the river rose by more than six metres (20 feet), and floodwaters were in some cases too powerful for emergency services to get through, even on boats, he said.

The River Aude, which flows through Carcassonne, Trebes and other towns, reached levels unseen since floods in 1891.

Television images showed water coursing through towns and villages, stranding cars and piling them on top of each other like children’s toys.

The French government rushed hundreds of rescue workers to the flood zone and helicopters buzzed overhead.