Some 300 firefighters have been battling the flames in the Monchique mountains for the last three days, with four villages evacuated on Monday as an uncontrolled wall of fire approached houses.

The mountains rise above the Algarve resort province, 250 kilometresmiles) south of Lisbon.

"It is a very worrying situation," said Jose Amarelinho, deputy mayor of Aljezur, the town closest to the evacuated villages.

He said the flames were advancing on a front of more than five kilometers (three miles) as about 300 firefighters backed by water-dropping aircraft fought to extinguish the blaze.

Rescue workers escorted residents away from the villages of Cerca, Moinho do Bispo, Marria Serrao and Monte Velho. Elderly residents were being sheltered in the fire department headquarters in Aljezur.

Authorities said that persistent high temperatures and a strong easterly wind helped spread the flames.

On Sunday, 300 people were evacuated from their homes in the nearby hillside town of Marmelete as the flames drew closer.

Rescue services director Gil Martins said on Monday that the situation around Marmelete was "much calmer".

More than 50 people have been arrested in Portugal in recent days for allegedly starting fires, while authorities suspect that 30 percent of the fires were started deliberately.

The arrest on Sunday of an alleged arsonist in the Algarve was followed Monday by the arrest of four people at Guarda in the northeast of the county. The four, in their twenties, were caught while trying to start a fire, the Lusa agency reported.

The Algarve receives the bulk of Portugal's summertime visitors and had, until Saturday, escaped damage from wildfires which have swept through the country since the end of July, killing 15 people and causing nearly one billion euros (1.1 billion dollars) in damage.

More than 200,000 hectares (494,000 acres) of woodland have been lost to flames so far this year, most of it since July, a forest service estimate released on Friday said.

But forestry experts, who have studied satellite images of the fire damage, told daily newspaper Publico on Sunday the total burnt area is likely to be at least 300,000 hectares.

TERRA.WIRE