Local Galician authorities announced they had made a series of arrests in connection with the fires, detaining two suspected arsonists after arresting three others overnight. One of that trio was later released.

Of the first two arrested, one was caught setting a blaze and the other reported by his neighbours for suspicious behaviour.

Another man was arrested late Tuesday at Lalin in the badly-affected Pontevedra region on suspicion of starting a blaze.

The defence ministry announced it was sending 1,200 troops to the region with 630 already mobilised to coordinate civil protection, along with four military planes.

Teams made up of firefighters and more than 3,500 forest workers, backed up by 30 aircraft, were battling 56 blazes in the northwestern, predominantly agricultural region of Galicia while a further 41 had been brought under control, despite strong winds.

Officials in Spain's southern region of Andalusia said they would send three planes to help while the eastern region of Catalonia, also hit by fires but to a far lesser degree, said it would send one.

Neighbouring Portugal, which is also struggling to contain wildfires amid scorching temperatures, meanwhile sent 66 emergency services workers and 19 vehicles late on Tuesday to Galicia to help the battle against the flames.

"Spain has helped us many times in the past. If there is a calamity in Portugal of course they will return," said. Interior Minister Antonio Costa.

Galician regional president Emilio Perez Tourino said most of the fires had been started deliberately.

The mayor of the worst hit area of Pontevedra, Miguel Anxo Fernandez Lobec, told Cadena Ser radio he was encouraging citizens to denounce the arsonists.

Spanish Environment Minister Cristina Narbona condemned those responsible, calling the fires "forestry terrorism".

She said she suspected some forestry workers had set fire to tinder dry land in anger at not being employed as auxiliaries over the summer by regional firefighting units.

Local officials have also cited "conflicts between ranchers and sheep farmers and landowners" over increasing grazing space and "behavioural problems" other possible causes.

The government passed a law banning immediate rebuilding on land devastated by fire after a similar spate of fires in 2005 believed linked to property speculation, a sector undergoing a huge boom in Spain.

The blazes in Galicia, several of them raging within metres (yards) of residential areas, came within two kilometres (1.2 miles) of the famous city of Santiago de Compostela, the end point of a historic pilgrimage trail.

The fires nearest the historic centre had been put out by Tuesday afternoon.

Three people have died in the fires. Two were engulfed as they tried to flee in their car and a pensioner was killed as he tried to douse the flames near his home.

In Portugal 11 forest fires were burning in the centre and north of the country late on Tuesday, battled by over 700 firefighters backed by over 200 vehicles, four of them out of control, the national firefighter service said.

Firefighters said they had managed to bring a blaze which had raged since early on Monday at Valongo, near the northern city of Oporto, under control due in part to a reduction in wind speeds.

Over 250 firefighters and 84 vehicles however were still at the scene of the blaze to guard against new flare-ups.

With temperatures forecast to rise above 40 degrees Celsius (104 degrees Fahrenheit) in some parts of Portugal over the coming days, the national firefighter service extended its "orange" fire alert level, the second-highest of four levels, until Friday.

Police in the central city of Guarda meanwhile announced they had detained a man in his late 20s who they suspect started a fire which raged on Monday in a wooded area near the town of Loringa.

The authorities are also investigating the possibility that a blaze, which destroyed some 4,000 hectares (10,000 acres) of eucalyptus forests near Estremoz in the southern Evora district on Monday, was started deliberately.

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