European nations sent firefighting teams to help France tackle a "monster" wildfire on Thursday, while forest blazes also raged in Spain and Portugal, and the head of the European Space Agency urged immediate action to combat climate change.

More than 1,000 firefighters, backed by water-bombing planes, battled for a third day a fire that has forced thousands from their homes and scorched thousands of hectares of forest in France's southwestern Gironde region.

With a dangerous cocktail of blistering temperatures, tinder-box conditions and wind fanning the flames, emergency services were struggling to bring the fire under control.