Brutal storms with winds gusting up to 224 kilometres per hour (140 miles per hour) left five people dead on the French Mediterranean island of Corsica early Thursday, including a 13-year-old girl who was killed when a tree fell onto her campground bungalow, authorities said.

It was the third day of intense rains across much of southern France that had produced flash floods and lightning, but left no casualties until now.

The girl was killed at a campground near Sagone, on the island's rugged western coast, where nine others were also injured, including one seriously, rescue workers told AFP.

At a nearby beach in Coggia, a 72-year-old woman died after the roof of a beachside hut was blown off and landed on the vehicle she was in, regional authorities said.

"I was woken around 7:30 am by a very huge storm" that knocked out both electricity and mobile phone networks, said Benjamin Roux, a 26-year-old tourist, at the beach near where the woman was killed.

He had been planning to go scuba diving, but instead helped the passengers of a boat who were sleeping aboard when it was suddenly thrown onto the shore by the choppy waves.

"They managed to get out without injuries, but they're just devastated," he told AFP.

Further north near the resort of Calvi, a 46-year-old Frenchman was also killed at a campground, and a 23-year-old Italian woman suffered serious injuries while camping nearby.

Maritime authorities later said a fisherman had died near Girolata, and a female kayaker near Erbalunga, north of Bastia.

"Several rescues of pleasure boats" were also undertaken near the capital Ajaccio, said Jean-Jacques Peraldi, head of the SDIS fire and rescue service.

Maritime authorities reported 60 to 70 sea rescue operations, mainly along the western coast that bore the brunt of the overnight storm, which the Meteo France weather service said was now moving towards Italy.

Authorities had urged people to avoid travel and take other precautions after storm alerts were issued Wednesday for several Mediterranean departments, but also along the Normandy coast and near the southeast city of Lyon.

Around 35,000 homes on Corsica remain without electricity, power provider EDF said.