Forest fires are raging in Portugal, Spain, France and Croatia, burning homes and threatening livelihoods as a wave of heat engulfed much of Europe, with temperatures rising to 40 degrees Celsius in some countries.

In Portugal's central region of Leiria, tired firefighters struggled with flames blown by strong winds. Footage from the area showed smoke obscuring the sky and rising over the highway, while flames licked the roofs of houses in one small village.

Across the border in western Spain, a fire that began Tuesday in the Extremadura region spread to the province of Salamanca in the Castile and Leon region, forcing the evacuation of 49 children from a summer camp Thursday. Regional authorities said more than 4,000 hectares of land had been burned.

The Spanish meteorological agency AEMET expects the heat wave to peak later Thursday, when temperatures are likely to exceed 44 degrees Celsius in much of southern Spain.

On Croatia's Adriatic coast, firefighting planes dropped water on burning forests, and troops were called in to help firefighters fight three major forest fires around Zadar and Sibenik.

In southwest France, about 1,000 firefighters backed by six planes fought two forest fires that began Tuesday.

The biggest of the two Gironde fires occurred around the town of Landiras, south of Bordeaux, where roads were closed and 500 residents were evacuated.

Thousands of people were also evacuated from homes in the southwestern Turkish peninsula of Datca as the fire, which began Wednesday, was blown by strong winds overnight and threatened residential areas.

A study published in Nature last week found that the amount of heat waves in Europe is increasing three to four times faster than in the rest of the northern mid-latitudes.