At least three people died, including a couple in their eighties, when thunderstorms hit southeast France on Tuesday, leaving behind what one official described as "scenes of war."

According to local authorities, the elderly couple died in the seaside town of Le Lavandou and one other person in the town of Vidauban.

The couple's vehicle was swept away by floodwaters.

The woman's body remained trapped inside the wreckage, said Toulon public prosecutor Samuel Finielz.

An investigation has been opened to determine the cause of death, he said, adding that "the situation was quite difficult on the ground."

Gil Bernardi, mayor of Le Lavandou, described "scenes of war," "roads torn up" and "bridges torn down."

"It was a really violent, vicious, incomprehensible phenomenon," Bernardi told BFM television.

"There is nothing left, no electricity, no drinking water, no sewage treatment plant," he added.

In Vidauban, a local official pulled a driver from her vehicle but the passenger could not be saved.

"A driver and her passenger drove onto a country road that was completely submerged" and the car fell into a ditch, the mayor, Claude Pianetti, said on Facebook.

Hailstorms and heavy rain also hit southwestern France a day earlier, flooding homes, damaging railway tracks and forcing the evacuation of hundreds of passengers aboard a high-speed TGV train in the middle of the night. (AFP)