With growing anger at the role of alleged arsonists in causing the devastation, police were questioning a 30-year-old man who they said had admitted responsibility for starting a previous wave of fires in the Var department two weeks ago.

The man, who was said to be disappointed at not having been taken on as a fireman, was spotted by several witnesses at the scene of the fires, police said.

The French government has promised to act without mercy against anyone found responsible for causing the region's worst forest fires in more than 25 years, with Justice Minister Dominique Perben warning that a sentence of life in prison was possible for arsonists who caused deaths.

Police, firefighters and local officials along the fashionable Riviera coast said that the simultaneous eruption of numerous blazes was an indication that organised bands were at work, and that petrol bombs had been found at some locations.

Perven said Tuesday that identity checks would be carried out at forests deemed at high risk in order to deter would-be arsonists.

According to the interior ministry in Paris, 25 separate fires were reported overnight on a 400-kilometre (250-mile) stretch from the Alps to the Pyrenees - a number it described as "highly surprising."

"This number does not even include the smaller fires of less than a hectare which also require manpower to put out," said Eric Souprat, spokesman for the civil security service.

However some officials warned against assuming the fires were of criminal origin, and said the vast majority were likely to have been started by human negligence or natural combustion at a time when the region is going through its severest drought in quarter of a century.

"The myth of the evil arsonist must not become a permanent alibi that lets everyone else off the hook," said Bernard Foucault, who is in charge of forest protection on the Mediterranean coast.

"The person who most often starts a fire is Mr or Mrs Everyman. It could be a farmer on a tractor who unknowingly sends out a spark, or a workman at a building site.

"The most annoying is the person who does not even realise what he risks when he lights his barbecue, or that the cigarette thrown from a car window can send everything up, or that a glass bottle can act like a magnifying glass," he said.

Wednesday morning around 700 firefighters aided by water-dropping aircraft were still battling a blaze which had consumed 1,500 hectares of brush around La Motte, about 20 kilometres (12 miles) from the coast, but they were confident they would bring it under control during the day.

Monday's devastating fires in the Maures hills nearer the shore had been subdued, though with forecasters warning of more hot weather and a Mistral wind of up to 80 kilometres an hour the emergency services remained in a state of high readiness.

On Monday four foreign tourists -- a 63 year-old British woman and her granddaughter, a 76 year-old Dutch woman and a 72 year-old Polish man -- were killed as the flames swept through the tinder-dry woodland. Another man died in fires on the island of Corsica.

Some 6,500 people who had to leave their homes and campsites for refuge in the municipal buildings in the coastal town of Frejus were allowed back Tuesday. Some villages remained without electricity, as power cables were switched off to allow water-dropping planes to operate in safety.

The scale of the fires has raised questions about the region's development. In recent decades highly-inflammable scrubland and pine woods have replaced farmers' terraces and pastures, while the population increase has led to large numbers of new houses.

TERRA.WIRE