Three men died and thousands were forced from their homes on Tuesday as wildfires fuelled by a heatwave scorched southern Europe.

Heat alerts were issued in Italy, France, Spain, Portugal and the Balkans, with temperatures expected to soar above 40C.

The heatwave is another sign of climate change, which is fuelling longer, more intense and increasingly frequent bouts of extreme heat.

"Thanks to climate change, we now live in a significantly warmer world," Akshay Deoras, a research scientist at the meteorology department in Britain's University of Reading told AFP, adding that "many still underestimate the danger".

An employee of a Spanish equestrian centre died from his injuries in Tres Cantos, a wealthy suburb north of Madrid, officials said – reportedly as he tried to save horses.

Later, officials in Castile and Leon in northwestern Spain confirmed another man had been killed while fighting fires.

And a soldier in the Balkan country of Montenegro died and another was seriously injured when their water tanker overturned while fighting wildfires in the hills north of the capital, Podgorica.

A child died of heatstroke in Italy on Monday.

The equestrian centre employee was the first fatality from dozens of wildfires that have hit Spain since a heatwave began last week.

Hundreds of residents of Tres Cantos fled from the fast-moving blaze, which was contained on Tuesday morning.

Spanish Prime Minister Pedro Sanchez said on X that rescue services were "working tirelessly to extinguish the fires" and warned: "We are at extreme risk of forest fires. Please be very cautious."

Elsewhere, about 2,000 people were evacuated from hotels and homes near the popular beaches of Tarifa in Andalusia, southern Spain.

The wildfire broke out near where a similar blaze forced evacuations earlier this month.

"We managed to save the residential area at the very last second," said Antonio Sanz, the Andalusia region's interior minister.

In Castile and Leon, dozens of blazes were reported, including one threatening Las Medulas, a Unesco World Heritage site known for its ancient Roman gold mines.

The head of the regional government of Castile and Leon, Alfonso Fernandez Manueco, vowed "to act quickly and generously" once the fire is over to restore the site "to its full glory as soon as possible".

In neighbouring Portugal, firefighters battled three large wildfires, with the most serious near Trancoso in the centre of the country. More than 700 firefighters were deployed there.

Temperature records were broken at four weather stations in southern France on Monday and three-quarters of the country was under heat alerts on Tuesday, with temperatures forecast to top 40C in the Rhone Valley. The Rhone department banned outdoor public events.

Temperatures started rising on Friday in France's second heatwave in just a few weeks and could remain high into next week, according to the national weather office Meteo-France.

Eleven Italian cities, including Rome, Milan and Florence, were placed on red alert on Tuesday due to the heat. (AFP)