More than 1,000 firefighters are battling a "monster" wildfire in south-western France that has already destroyed about 7,400 hectares (18,286 acres) of forest, officials say.
The blaze about 30km (19 miles) south-east of Bordeaux has gutted some homes and forced 10,000 residents to flee.
"It's an ogre, it's a monster," firefighter representative Gregory Allione told France's RTL Radio.
Strong winds and high temperatures are hampering the firefighting operation.
Sixty-five German firefighters have arrived from Bonn and others from Poland and Romania are expected in the fire zone soon.
"European solidarity at work!" President Emmanuel Macron tweeted.
France has nine water-bombing helicopters deployed and is also getting some firefighting aircraft from Greece and Sweden.
The wildfire in France's Gironde region has been raging for two days near the small town of Landiras.
In the same area last month a wildfire burned 14,000 hectares before being contained. It was France's driest month since 1961.
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.
A wildfire is now raging in the mountainous Serra de Estrela park in central Portugal, where 10,000 hectares of forest has been destroyed. The area is sparsely populated. About 1,500 firefighters are tackling the blaze.
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 probably affect health, transport and working conditions, the authorities warn.
In France some firefighters had to be urgently redeployed from other regions to boost the ongoing Gironde operation.
They are being backed by specialist aircraft dropping water and flame retardant.
But despite all the efforts, the blaze was still out of control on Thursday, local officials said.
Before the evacuation, some of the local residents had to save themselves on rooftops as the flames rapidly approached their houses, reports say.
Belin-Béliet is now a ghost town since all of its 2,000 inhabitants had to flee on Wednesday, BFMTV says.
In nearby Hostens, Allisson Fayol and her father - unlike many of their neighbours - decided to stay at home for now.
"There is still a lot of smoke but for now it's not coming this way," Ms Fayol was quoted as saying by Reuters news agency.
