More than 1,000 firefighters are battling a "monster" wildfire in the south-western France that has already destroyed nearly 7,000 hectares (17,300 acres) of forest, officials say.
The raging blaze near the city of Bordeaux has gutted a number of homes and forced 10,000 residents to flee.
"Its an ogre, its a monster," firefighter representative Gregory Allione told Frances RTL Radio.
Strong winds and high temperatures are hampering the firefighting operation.
This summer France and a number of other European countries have seen a wave of deadly wildfires, triggered by record temperatures and droughts across the continent.
More than 1,000 deaths have been attributed to the heat in Portugal and Spain.
In the UK, an amber extreme heat warning has now come into force, with temperatures forecast to hit 37C (99F) in some areas over the next four days. The heatwave will likely affect health, transport and working conditions, the authorities warn.
The huge wildfire in Frances Gironde region has been raging for two days near the commune of Landiras, about 30km (19 miles) south-east of Bordeaux.
A number of firefighters have had to be urgently redeployed from other regions to boost the ongoing operation.
They are being backed by specialist aircraft that have been dropping water and flame retardant.
But despite all the efforts, the blaze was still out of control on Thursday, local officials said.
"Its the first time weve seen a fire like this," French firefighter Jérôme Jean told BFMTV news website.
Before the evacuation, some of local residents had to save themselves on rooftops as the flames rapidly approached their houses, reports say.
Temperatures are expected to reach as high as 39C later on Thursday.
Prime Minister Elisabeth Borne and Interior Minister Gérald Darmanin are due to arrive to inspect the damage in the affected area.
Climate change increases the risk of the hot, dry weather that is likely to fuel wildfires.
The world has already warmed by about 1.2C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions.