NICE, France (AFP) - Violent storms and flooding along the French riviera killing 10 people and leaving six missing by early Sunday (Oct 4), emergency responders and local officials said, including three who drowned in a retirement home inundated when a river broke its banks.

Heavy flooding along the Cote d'Azur, in France's south-east saw the River Brague burst its banks close to the city of Antibes and sent deadly waves crashing into the nearby home for the elderly.

Water coursed through Cannes, Nice and Antibes, transforming the streets of three of France's most glamorous cities into debris-strewn rivers.

Three people died when water engulfed a retirement home at Biot near Antibes, and three drowned when their car was trapped by rising waters in a small tunnel at Vallauris-Golfe-Juan.

A woman in her 60s also died on the street in the resort city of Cannes when huge storms hit the region on Saturday night, sending water and debris coursing down submerged roads in the famous festival town and in its glamorous neighbour, Nice.

Another victim was found dead at an Antibes campsite, according to local officials.

Rescue teams at Mandelieu-la-Napoule, meanwhile, were searching for six people missing in underground carparks, according to emergency coordinators.

"Some cars were carried off into the sea," said Cannes Mayor Davis Lisnard, describing water levels reaching halfway up car doors and trees left uprooted on the city's main drag.

"We have rescued a lot of people, and we must now be vigilant against looting," he added, announcing that an emergency plan was now in effect to mobilise police, emergency responders and municipal services.

Cannes provided emergency shelter for 120 people, Mr Lisnard said.

President Francois Hollande and French Interior Minister Bernard Cazeneuve were expected to visit the site of the disaster, which occurred when the Cote d'Azur received up to 180mm of rain in just three hours.

Speaking on a visit to Japan, Prime Minister Manuel Valls said they were en route to the disaster zone.

Mr Cazeneuve would take stock of rescue efforts, his spokesman said.

Mr Hollande thanked rescuers and politicians for their work so far, expressing the "solidarity of the nation" and offering condolences to the families affected, while Mr Valls spoke of his "deep emotion" upon hearing of the deaths.

The areas worst-hit by flooding were also the hardest to access, officials said, raising fears the death toll could rise again, while 35,000 homes were confirmed to be without power.

French rail company SNCF said around a dozen trains had to be halted with hundreds on board for the safety of passengers, while roads around Antibes were also flooded, according to French emergency services.

"Camp sites are under water, and two helicopters are circling to ensure the public's security, as some people are stuck on the roof of their caravans," said a spokesman for the fire brigade.

Around 27,000 homes remained without power early on Sunday, 14,000 of them in Cannes alone. Communications to the region, which is one of the wealthiest in France and a magnet for visitors from around the world, were badly hit.

Up to 500 tourists, mostly British and Danish nationals, were stuck overnight at Nice airport.

About a dozen trains were halted at local stations. The state rail company SNCF provided food and blankets to hundreds of passengers who were stuck onboard.

The A8 motorway near Antibes was flooded when the Brague River burst its banks.

A Nice-Nantes match in France's first football division was called off in the 46th minute after the pitch became a quagmire.

France's weather agency said that 180mm of rain fell at Cannes between 7pm and 10pm on Saturday, with 159mm at Mandelieu-la-Napoule and 100mm at Valbonne.

Nice's mayor's office has estimated the city received 10 per cent of its average annual rainfall in the past two days alone.

By dawn, the worst storms had passed over the French mainland and were headed for the Italian coast, Meteo-France said.

The region's worst flood in the past 25 years was in June 2010, when 25 people were killed.

The worst national toll from flooding over this period was in January and February 1990, when 81 people were killed by violent storms in the north and west of the country.

In December 1999, 92 people in France were killed by flooding, fallen trees and other storm damage caused by hurricane-strength winds that struck north-western Europe.