Southern France is the latest area around the Mediterranean basin to be hit by wildfires this summer, a seasonal phenomenon which climate scientists warn will become increasingly common because of man-made global warming.
Large fires have already ravaged parts of Greece, Turkey, Spain, Portugal, Algeria and Morocco.
The blaze broke out Monday at a motorway stop about 100 kilometres (60 miles) northeast of the port city of Toulon.
By Tuesday morning, it had already covered more than 3,500 hectares of forest and scrubland, according to the fire department.
"This is the area covered but it is too early to estimate the area burned," the spokeswoman said.
Hot and arid southeast France, which regularly experiences summer wildfires, had been relatively spared so far this year.
According to the Prometheus database on forest fires in the Mediterranean region, the total area burned in France in the four regions hit was 2,336 hectares for 2021, against 7,698 for the whole of 2020.
Last year, a fire ravaged 1,000 hectares in a popular tourist region west of Marseille.
At least 2,700 people, including many tourists, had to be evacuated, some by sea.