PARIS - French "yellow vest" protesters occupied highway toll booths, setting a number on fire and causing transport chaos in parts of the country just days before the Christmas holidays getaway.

France's biggest toll road operator, Vinci Autoroutes, said there were demonstrations at about 40 sites along its network and that some highway intersections had been damaged, notably in tourist towns such as Avignon, Orange, Perpignan and Agde.

Protesters set fire overnight to the Bandol toll station, forcing the closure of the A50 highway between Marseille and Toulon, said Vinci, whose network is mainly in southern and western France. The Manosque station was also torched.

Some 20 people were arrested on Tuesday following the blazes, while four others remain in custody following fires on Saturday.

"Motorists should take utmost care as they approach toll gates and motorway access ramps due to the presence of numerous pedestrians," Vinci said in a statement.

Several people have died in roadside accidents at yellow vest roadblocks in recent weeks, mostly at the many roundabouts blocked by groups of demonstrators.

The "yellow vests" protesters - named after the fluorescent jackets French motorists must have in their cars - have blocked roads and roundabouts across France since mid-November.

The demonstrations began as a protest against fuel tax increases, but have morphed into a wider backlash against the liberal economic policies of French President Emmanuel Macron.

Protesters took to the streets of Paris and other cities on Saturday in a fifth weekend of demonstrations, though they were noticeably smaller than in previous weeks after Macron announced tax and salary concessions.

COSTLY DAMAGE

Protesters angry about high fuel costs and new speed limits have also damaged or torched hundreds of traffic radars.

Radars-auto.com estimated that by the middle of last week some 1,600 - about half of all French traffic radars - had been damaged. More than 250 have been entirely destroyed, it said.

The French state will also lose several tens of millions of euros in revenues, it said, adding that in 2017 the radars had yielded on average 84 million euros ($96 million) per month.

The interior ministry declined comment on the number of radars damaged, but said that minor damage cost on average 500 euros per radar to repair, with major damage costing up to 200,000 euros.

Fines for damaging radars can run as high as 75,000 euros.

"Even wrapping a radar in plastic or a yellow vest... without destroying it is an offence," a ministry official said.

Vinci estimates the damages since the start of the protests will cost it "several tens of millions" of euros, not including lost revenue, as the protesters have allowed thousands of motorists onto the highways for free.

It dropped a plan to send invoices to motorists who drove through toll booths without paying and whose licence plates were captured on cameras following government criticism. ($1 = 0.8792 euros)

Reuters