More than 300 firefighters backed by 70 vehicles were battling the blaze which erupted near Mafra, some 40 kilometres (25 miles) northwest of Lisbon, just after noon, forcing the closure of several roads.

Local fire chief Joaquim Moureira Vicente said strong winds were fueling the fire and making it difficult to use four water-dropping aircraft at the scene.

"We are putting on a muscular attack, but the wind is coming from every direction which is making it very difficult," he told state radio RDP.

He said eight firemen were treated for smoke inhalation in addition to the five who suffered burns.

The flames had entered a 17 hectare (42 acre) refuge which is home to 17 Iberian wolves, a species facing extinction in Portugal.

"We are alarmed because the wind changed direction and the fire, which seemed contained, is now out of control," Francisco Petruki told private news radio TSF.

Efforts were being made to evacuate the animals to a zoo in Lisbon, he said.

Once found across the country, environmentalists estimate there are now only some 300 Iberian wolves in the wild in Portugal, mostly in the north.

The wolf refuge was set up in 1989, one year after the government passed legislation to protect the endangered animal.

The blaze has already destroyed dozens of acres of brush and eucalyptus forest in a region that was badly affected by a wave of wildfires which swept Portugal in 2003, killing 20 people and burning a record amount of land.

Civil protection officials said most of mainland Portugal, which is facing its worst drought in decades, suffered from a high risk of wildfires on Monday because of soaring temperatures and low air humidity levels.