Hurricane-force winds lashed southern France on Sunday, damaging a ferry off Marseille and leading to the disappearance of two people, including a British boy who was out cycling.

Winds packing up to 130 kilometres (80 miles) an hour battered several areas in the south, including the coastal region of Herault, where a 12-year-old British boy and a windsurfer were reported missing since Saturday.

Heavy snow in the French Alps meanwhile caused power cuts to more than 50,000 households and created traffic snarls as cars were blocked on roads in a busy weekend leading up to All Saints' Day.

The strong winds in the south badly damaged a large ferry owned by the National Corsican Company, the "Napoleon Bonaparte", which crashed against the dock.

The flooded vessel, which can carry 2,650 passengers and 708 vehicles, was still tilted on one side in the harbour on Sunday afternoon and was waiting to be "stabilised", Hugues Parant, the prefect of Marseille, told AFP.

In the nearby Herault region, the missing British boy's cycle was found and he was thought to have been "swept away" by the strong winds, said Xavier Tarabeux, the prosecutor of the southern port city of Toulon.

The boy went missing in the tourist town of Hyeres on Saturday, said its mayor, Jacques Politi. The 12-year-old, whose mother is French, had just arrived with his parents and siblings to spend the holidays.

A 26-year-old windsurfer was also missing at a nearby beach. Search operations were on, with police teams and firefighters as well as locals scouring the area, backed up by a helicopter to trace the missing.

The winds felled trees and about 5,000 households in the area had no power supplies due to snapped transmission lines.

Heavy snow on Sunday blanketed the French Alps and more than 50,000 houses had no electricity, the state power supplier said.

Forty cars were blocked in the Alpine Isere region as they were not equipped with snow tyres, officials said. Those stranded overnight were housed in a nearby gymnasium.

burs-ach/jhb