France on Tuesday declared a state of natural disaster in about 60 southern towns hit by torrential downpours, which also left the Mediterranean city of Montpellier under water.

Floodwater streamed down roads and highways, engulfing cars as the Lez river burst its banks in the seaside capital of the Languedoc-Roussillon region after it was lashed by record-breaking downpours.

"In a few hours Montpellier had the equivalent of half a year's worth of rain," Meteo-France weather services told AFP, adding the 300mm (nearly 12 inches) which fell on Monday broke all records, which date back to 1957.

More than 4,000 people across the rain-soaked region spent the night in emergency centres and schools or stuck in train stations and airports, the local government said in a statement.

According to the municipality, emergency workers were called out more than 1,200 times, backed up by three helicopters.

"We will put in place natural disaster measures for about 60 towns," Interior Minister Bernard Cazeneuve told local media, adding he would head to the flood-hit region later Tuesday.

Rains were expected to ease Tuesday and meteorologists downgraded the maximum red alert to orange.

No deaths have been reported from the latest round of storms to lash the Herault region, where four people died when a flash flood swept through their campsite 10 days ago.

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