Portugal's Algarve tourist region is the latest to be hit by violent forest fires, prompting the evacuation of a luxury hotel and three hamlets, officials said.

Over 2,700 firefighters backed by water-dropping aircraft were trying to get some 100 blazes under control across the country, despite a respite from the intense heat of recent days.

About 50 tourists, including many British nationals, were evacuated from a hotel just north of the coastal town of Portimao in the southern Algarve region because of the threat from the flames.

"The fire was very close, there was a lot of smoke, but the flames spared the hotel," the hotel's director, Rui Covas, told AFP.

Officials evacuated about 30 people from three nearby hamlets because of the blaze, which broke out in the wooded hills around the mountain town of Monchique and then moved south towards the coast.

Vitor Vaz Pinto, head of emergency services there, said that after dying down, the fire had re-started on Wednesday evening "in an explosive manner".

"It's hell," a local resident said on Portuguese television.

"I don't know if someone set fire to the area, or if the wind fanned the flames."

The Algarve, which is known for its sandy beaches and golf courses, is one of Europe's top vacation spots.

In the north, meanwhile, a large-scale blaze was raging in the Douro International Natural Park, near Freixo de Espada a Cinta on the border with Spain.

"We have had to evacuate a retirement home, the flames came very close," said Joao Possacos, mayor of the affected village of Bruco.

Across the border in Spain to the northwest, firefighters and water-dropping aircraft continued to battle four blazes, forcing the evacuation of several houses.

Other fires continued in the north and southwest of Spain.

But Agriculture Minister Isabel Garcia Tejerina has played down the scale of the fires this year.

According to her ministry, wildfires destroyed almost 100,000 acres of land between January and August - an area close to the size of Barbados.

Many of the fires are suspected to be the work of arsonists.

On Thursday, a man was arrested in a natural park in the southern Spanish region of Andalusia, suspected of having set paper and plastic bags on fire to try to spark a blaze near the small town of Almaden de la Plata.