In the town of Villegailhenc, witness Ines Siguet said the waters rose so quickly that people were stranded on the roofs of their homes and had to be helicoptered to safety.
Residents look from their window above cars standing in a flooded street following heavy rains that saw rivers bursting banks in Trebes, near Carcassone, southern France, on October 15, 2018.
In total nine residents died in the city, which made headlines earlier this year after a jihadist attacker killed four people in a shooting spree, including a police officer who took the place of a hostage.
The French leader is expected to travel to the Aude region in coming days to see the damage and to meet with affected residents floods.
Flash floods tore through towns in southwest France, turning streams into raging torrents that authorities said killed several people and seriously injured at least five others. The Interior Ministry and Aude officials put it at 12 after two more bodies were recovered in the towns of Trebes and Carcassonne. "It was very violent". Local residents have been told to remain indoors. 'She thought she was safe behind locked doors and windows, but the water burst in'. I go to the kitchen, I open the door.
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Helene Segura, who lives in Villegailhenc, described the view from her home: "When I look out the window, I can only see water and mud everywhere. I was terribly afraid".
National emergency services spokesman Michael Bernier said 13 people had been killed and one person was still missing.
Television images showed water coursing through towns and villages, stranding cars and piling them on top of each other like children's toys. At least one person was swept to their death while they slept.
The French government rushed hundreds of rescue workers into the flood zone and helicopters buzzed overhead. The official asked for anonymity because he was not authorized to speak publicly.
The floods are the worst to have hit the Aude river in more than 100 years, reported the BBC, quoting French weather monitoring service Vigicrues.
France's interior ministry says the government has fully mobilized to help in the crisis; it's also warning people to stay off roads and to try to limit their use of phones, to allow emergency operators to use the limited capacity that's available.