Large wildfires raging near the Greek capital Athens have forced thousands to evacuate, with flames reaching heights of 25 meters, as much of Europe contends with extreme heat conditions.

Italy endured intense temperatures over the weekend and French authorities issued weather warnings for southern areas of the country.

The United Kingdom was bracing for its hottest day of the year so far on Monday, with temperatures in some areas set to reach above 34 C.

High temperatures and strong winds fueled a massive wildfire north of Athens, where more than 400 firefighters, supported by aircraft, battled flames that burned trees, houses and cars and sent smoke clouds billowing over the capital, Reuters reported.

The fire brigade described attempts to combat the flames as "superhuman". Evacuation orders expanded on Monday, with at least five more communities instructed to leave, adding to the hundreds of people who had already fled from at least eight villages on Sunday, the BBC reported.

"The situation remains dangerous as the fire is spreading between residences," said fire brigade spokesperson Vassilios Vathrakogiannis, noting that the fire spread "like lightning" because of strong winds.

In Varnavas, a village of about 1,800 people that is 35 kilometers north of Athens, flames swallowed up trees and shrub land.

Civil Protection Minister Vassilis Kikilias cautioned that high temperatures, strong winds and drought conditions had put half of the country at significant risk for wildfires. Greece's Prime Minister Kyriakos Mitsotakis returned to Athens from his holiday to address the situation.

The historic town of Marathon, east of Athens, was among those evacuated on Sunday.

"Everything is burning," Giorgos Tsevas, a resident of nearby Polydendri village, said. "I have 200 olive trees there, but now they are gone."

Climate experts attribute the current extreme temperatures primarily to human-caused global warming.

The World Health Organization has cautioned about the serious effects of increasing temperatures on European populations, noting that as the continent warms faster than any other, heat-related causes claim an estimated 175,000 lives annually.

Rome has been experiencing a continuing heat wave since the beginning of last month, with temperatures persistently above normal levels.

Cited by Euronews, meteorologist Lorenzo Tedici from Italy's Il Meteo weather forecasting service emphasized the link between fossil fuel use since 1850 and planetary heating.

"These 21st-century anomalous heat waves are unfortunately caused by the anthropogenic greenhouse effect," he said.