"This is a very serious moment for Portugal," Sampaio told reporters during a visit to the headquarters of the national fire service near Lisbon.

With Portugal enduring its worst drought since the 1940s, some 3,200 fire-fighters backed by 800 vehicles and 30 aircraft were fighting the blazes with the help of hundreds of military and police.

Sampaio appealed to employers to release volunteer firemen from their work obligations "because at this time the country needs as many fire fighters as possible."

Earlier, Prime Minister Jose Socrates acknowledged that the country was running out of resources to fight the fires and said he had invoked a European Union mechanism for cooperation in emergencies.

"We have asked the European Union for reinforcements because yesterday the resources we had at our disposal were no longer enough to fight all of the fires," Socrates said in the central district Pampilhosa da Serra, where 30,000 hectares (74,000 acres) have been burnt.

France and Spain were the first to respond to the appeal. A Spanish plane was already in operation in the north of Portugal while a second plane was dispatched to Pampilhosa da Serra later Sunday.

Two aircraft have been sent by France while three heavy helicopters from Germany were to arrive Monday, along with 25 firefighting experts.

Italy said it was immediately sending a Canadair aircraft and was weighing the possibility of sending a larger Beriev BE200 amphibious turbojet, which is capable of dropping 12,000 liters of water. The plane was in operation against a fire in Sardinia, said a spokesman for the Italian civil defense, but could leave for Portugal on Monday.

The president of the European Commission, Jose Manuel Barroso, who was on vacation in northern Portugal, visited some of the fires, a spokesman said.

French Interior Minister Nicolas Sarkozy meanwhile called for greater cooperation between the emergency services of EU countries in disaster situations.

His Portuguese counterpart Antonio Costa said that weather conditions over much of his country -- suffering its worst drought since 1945 -- were "very bad". "In this type of situation, there are never enough resources," he said.

The Portuguese were also calling on additional internal resources, mobilising 2,000 members of the national gendarmerie force (GNR) to evacuate people, close highways threatened by fire and keep roads clear for fire trucks and ambulances, a GNR spokesman told Lusa news agency.

The fires were being driven by 40-mile-an-hour (70-kilometer-an-hour) winds and some were in rugged inaccessible terrain.

Several dozen people had to be evacuated from their homes in the Pampilhosa da Serra area. Fire fighters said they heard "little explosions" which led them to suspect the fires may have been deliberately lit.

The situation was also critical at Abrantes, not far from Pampilhosa, where a number of houses were threatened by the fire.

Firefighters and local authorities suspect arson in the wave of fires which have so far killed 10 firefighters and burnt 134,500 hectares (332,000 acres) of forest and scrub land since the beginning of the year. Some 95 people have been arrested by police in Portugal this year and face arson charges.

Of the 18 districts in Portugal, 16 were on "maximum" or "very high" fire alert.

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