Five water-dropping aircraft and more than 200 firefighters were at the scene of the biggest blaze near Albergaria-a-Velha, some 250 kilometresmiles) north of Lisbon, emergency services workers said.

The wildfire led local authorities to close a stretch of the nation's main highway, linking Lisbon to second-city Oporto in the north, for over seven hours because of the heavy smoke and threat to vehicles from the flames.

Local residents scrambled to protect their homes by using buckets of water and tree branches to put out the flames, images on state television RTP showed.

"Firefighters have the fire in their hands, it is getting controlled," the mayor of Albergaria-a-Velha, Joao Agostinho, told the television station.

"We could have had a catastrophe here," he added.

Firefighters suspect arsonists may be responsible for the blaze, which erupted in the early hours of Friday and was fueled by winds of up to 120 kilometres (75 miles) and hour, the mayor added.

Further north firefighters in the district of Oporto were battling some 30 wildfires of various sizes.

The fires caused ashes to rain down on downtown Oporto, private radio TSF reported.

Local officials said they had asked the army for help in the battle against the wildfires, which come as Portugal is facing its worst drought in decades.

Wildfires destroyed 21,504 hectares (53,115 acres) of brush and forest during the first six months of the year, compared with an average of 15,751 hectares during the past five years, agriculture ministry figures show.

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