Firefighters in north-western Spain are battling more than 100 fires that have already devastated some 10,000 hectares (24,700 acres) of land, officials say.
Many residents have joined firefighters to protect their homes
Some 1,200 soldiers are being deployed in the Galicia region to try to put out the blazes and co-ordinate evacuations.
Three people have died in the fires that have been raging since last week. High winds and dry weather are said to be making conditions worse.
Five suspected arsonists have been arrested. One has been freed on bail.
A number of fires are also ravaging the north-eastern region of Catalonia and northern regions in neighbouring Portugal.
Some 110 fires were burning in wooded areas of Galicia on Wednesday, officials said.
Firefighters - helped by some 30 fire-fighting planes - had managed to get 49 fires under control, local government spokeswoman Iria Mendez said.
But high winds and dry weather conditions were boosting more than 60 blazes, she said.
Although Galicia suffers from forest fires every year, this year's destruction has been described as "unprecedented" by local officials, according to the AFP news agency.
Spanish Environment Minister Cristina Narbona earlier this week urged people to denounce arsonists to the authorities so their crimes did not go unpunished.
She said some of the fires could have been started by forestry workers angry at not being drafted over the summer by the regional fire-fighting brigades.
In the past, similar fires were blamed on property developers trying to clear land. Last year Spain passed a law banning immediate rebuilding on scorched land.
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