A military firefighter has been killed and three others injured in a crash as hundreds of firefighters backed by aircraft struggled to tame a wildfire in western Spain, emergency workers said.

A Red Cross statement said a truck belonging to the army's emergency services unit, which was assisting the firefighting effort on Saturday, overturned and crashed about 300m down a hillside. One of those injured was in a serious condition.

The fire erupted on Friday night in the Extremadura region near the Portuguese border and was so fierce that authorities quickly cleared 300 people from a camping site in Gata, local officials said.

The regional authority said in a statement that efforts to douse the fire were hampered by wind gusts blowing up to 45 kph.

By Saturday, officials had deployed 13 helicopters and seven firefighting aircraft to back the approximately 450 firefighters - both military and civilian - on the ground who were battling the blaze on two fronts.

As night fell, local officials said the blaze was stabilising and they had withdrawn the aircraft from the operation.

Firefighters on the ground would keep working through the night, using trucks, bulldozers and fire breaks to ensure the blaze did not flare up again, officials added.

A regional government spokesman could not say how much territory had been burned, but this summer's forest fires in Spain have been particularly violent.

Late on Saturday, authorities said another fire had broken out on the Canary island of La Palma near the town of Mazo. That blaze had chewed through about 340 hectares.

Two smaller fires also broke out on the island of La Gomera.

After a winter that saw almost no rainfall, the Spanish landcsape was left drier than ever in seven decades.

On July 22, a wind-whipped wildfire in the northeast province of Catalonia near the border with France scorched 14,000 hectares, claiming four lives.

Spain's most destructive fires so far this year were in the Valencia region in early July, burning some 50,000 hectares of vegetation.