Firefighters battled to contain wildfires sweeping across southwest Europe on Sunday as a heatwave showed no sign of abating, with Britain poised to set new temperature records this coming week.

Blazes raging in France, Greece, Portugal and Spain have destroyed thousands of hectares of land and forced thousands of residents and holidaymakers to flee.

It is the second heatwave to engulf parts of southwest Europe in weeks. Scientists blame climate change and predict more frequent and intense episodes of extreme weather such as heatwaves and drought.

Almost the whole of Portugal is on high alert for wildfires
Almost the whole of Portugal is on high alert for wildfires AFP / PATRICIA DE MELO MOREIRA

Spanish authorities reported around 20 wildfires still raging out of control in different parts of the country from the south to Galicia in the far northwest, where blazes have destroyed around 4,500 hectares of land.

The fires have already killed several emergency personnel since last week, most recently a fireman who died late on Sunday while battling a blaze in northwestern Spain.

In France, the situation deteriorated in the southwestern Gironde region where firefighters were fighting to control forest blazes that have devoured nearly 11,000 hectares (27,000 acres) since Tuesday.

Scientists say extreme weather is becoming more frequent and more intense due to climate change
Scientists say extreme weather is becoming more frequent and more intense due to climate change AFP / Patricia De Melo MOREIRA

The wildfires in France forced more than 16,000 people -- residents and tourists combined -- to decamp. Seven emergency shelters have been set up for evacuees.

France's interior ministry announced it would send an extra three firefighting planes, 200 firefighters and more trucks.

Meteo France forecast temperatures of up to 40 degrees Celsius (104 degrees Fahrenheit) in parts of southern France on Sunday, with new heat records expected on Monday.

Heatwave in Europe
Heatwave in Europe AFP / Kenan AUGEARD

"In some southwestern areas, it will be a heat apocalypse," meteorologist Francois Gourand told AFP.

France placed 15 departments, mainly down its western seaboard, on red alert -- the highest on the scale -- on Sunday while 51 were on orange high alert.

The chapel of a historic hospital in the southeastern city of Lyon, Grand Hotel Dieu, offered refuge to tourists on Sunday including Jean-Marc, 51, who was visiting from Alsace.

"We came back to admire the place, but we can't leave, it's too hot outside. We say a prayer before the fire!" he quipped.

The UK weather office has issued a first-ever "red" warning for extreme heat
The UK weather office has issued a first-ever "red" warning for extreme heat AFP / Oli SCARFF

French cyclist Mikael Cherel, taking part in the Tour de France's 15th stage between Rodez and Carcassonne in southern France on Sunday, described "very, very difficult conditions".

"I've never known such a hot day on a bike. It really was no picnic."

Advice for elderly people, children and adults on how to cope in a heatwave
Advice for elderly people, children and adults on how to cope in a heatwave AFP / Cléa PÉCULIER

In Spain, firefighters managed to stabilise a wildfire that ravaged 2,000 hectares of woods and bushes in the southern region of Andalusia, regional leader Juan Manuel Moreno said.

The blaze started on Friday in the Mijas mountain range inland from the southern coastal city of Malaga and it spurred the evacuation of about 3,000 people.

Around 2,000 people had since returned home and now that the blaze has stabilised, Moreno said the remaining evacuees may do the same.

A fireman died from burns on Sunday while battling a blaze in Spain's northwestern province of Zamora, the regional government said.

Spanish Prime Minister Pedro Sanchez expressed his "condolences and affection" to the man's family and colleagues.

"There are no words to express thanks to those who fight fires without rest for their immense work. RIP," he added in a tweet.

Sanchez is due to visit the hard-hit eastern region of Extremadura on Monday where various fires have been raging for days.

The fireman's death comes after a pilot was killed last week when his plane crashed in northern Portugal, and two crew members died in Greece when their helicopter fell into the sea.

The extreme heat also claimed the lives of two men in Spain over the weekend.

A 50-year-old man in Torrejon de Ardoz just outside of Madrid died on Sunday after suffering heat stroke while out for a walk, local emergency services said.

And on Saturday, a 60-year-old street cleaner in Madrid died after suffering heat stroke while working the previous day.

In Portugal, almost the entire country remained on high alert for wildfires despite a slight drop in temperatures, after hitting 47C -- a record for the month of July -- on Thursday.

Only one major fire was burning on Sunday in the north.

The fires have killed two, injured around 60 and destroyed between 12,000 and 15,000 hectares of land in Portugal.

In the United Kingdom, the weather office issued a first-ever "red" warning for extreme heat, cautioning there was a "risk to life".

Organisers of a four-day march in the Netherlands cancelled the first day of the mass event due to start on Tuesday because of extreme heat.

The mercury is set to reach 38C in parts of the Netherlands on Tuesday.