Wildfires tore through parts of France, Spain and Portugal on Thursday as heatwaves baked Europe and the head of the European Space Agency urged immediate action to fight climate change.

More than 1,000 firefighters, backed by water-bombing planes, battled for a third day a "monster" blaze that has forced thousands from their homes and scorched thousands of hectares of forest in France's southwestern Gironde region.

With a dangerous cocktail of blistering temperatures, tinder-box conditions and wind fanning the flames, President Emmanuel Macron said several European Union nations were deploying reinforcements to help beat back the blaze.

"It's an ogre, a monster," said Gregory Allione from the French firefighters body FNSPF said.

Heatwaves, floods and crumbling glaciers in recent weeks have heightened concerns over climate change and the increasing frequency and intensity of extreme weather across the globe.

The head of the European Space Agency, Josef Aschbacher, said rising land temperatures and shrinking rivers as measured from space left no doubt about the toll on agriculture and other industries from climate change.

ESA's Copernicus Sentinel-3 satellite series has measured "extreme" land surface temperatures of more than 45C (113F) in Britain, 50C in France and 60C in Spain in recent weeks.

"It's pretty bad. We have seen extremes that have not been observed before," Aschbacher told Reuters.

CLIMATE CHANGE RISKS

With successive heatwaves baking Europe this summer, bringing record temperatures and unprecedented droughts, renewed focus has been placed on climate change risks to farming, industry and livelihoods.

Severe drought is set to slash the European Union's maize harvest by 15%, dropping it to a 15-year a low, just as Europeans contend with higher food prices as a result of lower-than-normal grain exports from Russia and Ukraine.

Swiss army helicopters have been drafted in to airlift water to thirsty cows, pigs and goats sweltering under a fierce sun in the country's Alpine meadows.

In France, suffering its harshest drought on record, trucks are delivering water to dozens of villages where taps have run dry, nuclear power stations have received waivers to keep pumping hot discharge water into rivers, and farmers warn a shortage of fodder may lead to milk shortages.

In Germany, scant rainfall this summer has drained the water levels of the Rhine, the country's commercial artery, hampering shipping and pushing freight costs.

However, as Europe contends with another heatwave, one group of workers has little choice but to sweat it out: gig-economy food couriers who often fall between the cracks of labour regulations.

After the mayor of Palermo on the island of Sicily in July ordered horses carrying tourists be given at least 10 litres of water per day, bicycle courier Gaetano Russo filed a suit demanding similar treatment.

"Am I worth less than a horse," Russo was quoted as saying in a Nidil CDIL union statement.

"HEARTBROKEN"

Britain's Met Office on Thursday issued a four-day "extreme heat" warning for parts of England and Wales.

In Portugal, more than 1,500 firefighters spent a sixth day fighting a wildfire in the central Covilha region that has burned 10,500 hectares (40 square miles), including parts of the Serra da Estrela national park.

In Spain, electrical storms triggered new wildfires and hundreds of people were evacuated from the path of one blaze in the province of Caceres.

Macron's office said extra fire-fighting aircraft were arriving from Greece and Sweden, while Germany, Austria, Romania and Poland were all deploying firefighters to help tackle wildfires in France.

"European solidarity at work!" Macron tweeted.

Firefighters said they had managed to save the village of Belin-Beliet, which turned into a ghost village after police told residents to evacuate as the flames approached, but that weather conditions would not help containing the blaze.

The Gironde was hit by big wildfires in July

"The area is totally disfigured. We're heartbroken, we're exhausted," Jean-Louis Dartiailh, a local mayor, told Radio Classique. "(This fire) is the final straw.