SOULAC-SUR-MER, France (AFP) - On the ground, two officers from a special mobile brigade of France's paramilitary gendarmerie speed along a forest track.

Above them, a helicopter scans the landscape to warn them of any fires or anyone who might be looking to start one.

These are the members of a newly created police team who have just started patrolling in south-west France to seek out and arrest the fire-starters devastating the region's forests.

In the last week, no less than 20 fires have broken out in the forest bordering the seaside resort of Soulac-sur-Mer in the La Gironde department of south-west France, says the local gendarmerie.

While some have burned just 100 sq m, the largest devoured 30ha of forest.

Scorched trees and charred trunks line the paths and cycle paths that criss-cross the woods.

To stop the devastation, local officials have sent in the new unit, the Forest Vigilance Platoon (PVF), made up of 15 reservist gendarmes, a senior police officer and two motorcyclists from the mobile brigade, backed up by the helicopter.

Spread across three zones, the PVF patrol the forest on motorbikes, all-terrain bicycles or in cars, where possible, on the hunt for fire-starters.

Set up just last week they started patrolling last Thursday (Aug 11).

The idea is that the PVF will free up firefighters who have been stretched thin battling blazes that since last Tuesday have burned up 7,400ha of pine forests at the southern end of Gironde.

"After the major fires in July, we observed a rise in the number of arson cases," said Mr Martin Guespereau, deputy prefect for defence and security in the Nouvelle-Aquitaine region, which covers the Gironde.

"There are around 20 fires of unknown origin a day in Gironde."

According to France's National Forests Office (ONF), nine out of 10 fires were started by people - and three out of 10 were started deliberately.

Forest off-limits

"The Forest Vigilance Platoon is a support division, whose aim is to prevent, detect and possible to arrest," said Captain Christophe Roque, who was given the job of putting the team together.

Red-and-white signs at the edge of the Soulac-sur-Mer forest inform walkers that due to the "very severe" risk of fire, the forest is off-limits to the public until further notice - and has been since Aug 11.

A few cyclists were nevertheless out on the trails on Saturday, and were quickly intercepted by the gendarmes of the PVF.

"As soon as we come across someone, we get their identity," said one member of the team, Mr Bruno Kechtoff. "Because if we come across the same person several times, then that becomes suspicious."

A message comes over the radio: two outbreaks of fire barely 500m apart, near Bazas, south of Bordeaux, the regional capital. A local has reported seeing someone on a moped wearing "yellow-trimmed" trousers".

The LVF's helicopter veers off towards Bazas, 130km away away.

Where they are sent next depends on where the next fires break out, says Constable Jeremy Hernandez. "We have been called here urgently but we can move if other areas are concerned."

Then they are in their car and driving off, siren wailing, on the lookout for a quad reported in the woods.