Spanish firefighters on Saturday struggled to contain wildfires that have ravaged large tracts in the northwest, as a third summer heat wave grips the country.

Firefighters were battling six blazes in Galicia that have scorched nearly 3,000 hectares (7,400 acres).

Some 700 people have been evacuated from the area around Boiro, where a blaze broke out on Thursday, according to regional officials.

But no casualties have been reported so far.

"The situation remains complicated. Helicopters are not enough to control all of the homes," the mayor of neighbouring A Pobra do Caraminal, Xose Lois Pinero, wrote on Facebook.

Near the town of Verin, by the border with Portugal, authorities were managing to contain a fire that started Wednesday and is suspected to have been arson, Galicia government said.

Temperatures hit a 40.9 degrees Celsius (105.62 Fahrenheit) high on Thursday, according to the national weather agency. They have eased since, but were expected to remain around 35C across much of the country on Saturday.

Scientists say human-induced climate change is making extreme weather events including heatwaves and droughts more frequent and more intense. They in turn increase the risk of fires, which emit climate heating greenhouse gases.

Spain has faced 366 wildfires since the start of the year, fuelled by scorching temperatures and drought conditions.

The flames have destroyed more than 233,000 hectares, more than in any other nation in Europe, according to the European Union's satellite monitoring service EFFIS.