France, which widened its heatwave red alert in the south of the country, said it would scale back production at a nuclear power plant as high temperatures curbed cooling water supply.

In Greece, firefighters battled a blaze for a second day close to Athens, and authorities warned that heat and winds risked stoking more wildfires a day after 18 bodies, probably migrants, were found in a charred northern forest.

A wildfire north of Athens that erupted on Tuesday has smothered the capital in smoke and ash, spreading to the town of Menidi, where about 150 people were evacuated from three nursing homes. Police ordered others to leave as a helicopter clattered overhead to drop water onto the conflagration.

"The fire went out for half an hour.... but with these very strong winds, it's been alternately starting and then stopping again," 60-year-old resident Dimitris Armenis told Reuters.

A volunteer carried an icon of the Virgin Mary out of a burning monastery, while police raced to remove large gas canisters from the ash-covered premises.

Another 700 people were moved from a migrant camp in the Amygdaleza region, about 25 km (16 miles) north of Athens, a Migration Ministry official said.

Greek Climate Crisis and Civil Protection Minister Vassilis Kikilias said 355 wildfires had broken out since Friday, with 209 new blazes in the last 48 hours alone.

Near the northeastern Greek port city of Alexandroupolis, dozens of hospital patients, some on stretchers, others attached to IV drips, were evacuated onto a ferry as a fire in the area blazed for a fifth day.

Authorities were trying to identify the 18 bodies discovered on Tuesday in Dadia forest in the Evros region on Turkey's border, on a common route for migrants from the Middle East and Asia trying to cross into the European Union.

SHIPPING DISRUPTED

On the Turkish side, Turkish President Tayyip Erdogan said on Wednesday crews had stopped the Canakkale fire's spread and it would be under control shortly. He said more than 150 ships were halted on the Dardanelles Strait to allow helicopters and planes to scoop up water to contain a forest fire in the area that was raging for a second day.

The strait, linking the Aegean Sea and the Black Sea, is a major shipping route for commodities such as oil and grains.

The French national weather service, Meteo-France, reported the country's highest average temperature for the late summer period after Aug. 15 since records began in 1947. It said some areas of southern France would experience temperatures of 42 degree Celsius (108 degrees Fahrenheit).

French power producer EDF issued a production warning for the Saint Alban nuclear power plant on the Rhone river because of a shortage of cooling water. Similar warnings have been issued this summer for other plants.

The heatwave has even reached the region's highest peak, Mont Blanc with authorities urging climbers to delay their ascent because of an increased risk of rock falls and new crevices on glaciers from melting snow.

"It has definitely changed in that time and routes are changing ... you can almost see it, just melting away very slowly," said Australian alpinist Daniel Trevena, who has been coming to the region for 10 years.

In Spain, which is enduring its fourth heatwave of the summer, people who normally receive food and other necessities from the non-governmental organisation Fundacion Madrina were also handed fans on Wednesday to cope with high temperatures.

In Madrid's El Rastrillo square, fashion worker Daniela said she was struggling to keep cool: "I’m really hoping it is over, this is the last heatwave."

Firefighters on the Spanish island of Tenerife brought under control a blaze that devastated forests, allowing about 8,000 evacuees to return.

But local farmers protested about the use of scarce water resources to fight the blaze and police said they had arrested an 80-year-old man for throwing stones at a firefighting helicopter, forcing it to make an emergency landing.

Italy issued heatwave red alerts about "emergency conditions" that the health ministry says could endanger the healthy, as well as those who are frail, in 17 of its 27 main cities for Wednesday and Thursday, including Rome, Milan, Florence and Venice. The number was set to rise to 19 on Friday.