Gang members posing as policeman duped their victims into thinking that a routine check was being carried out.

The looters were equipped with cars bearing police insignia and a revolving amber light.

Favourite targets of the gang were foreign plated cars carrying tourists taking a break at one of the rest areas on the motorways.

The attacks normally took place during the hours of darkness, with victims woken from a sleep with a request for an examination of their papers.

They were then asked to open up the boot of the vehicle for check of the contents, when they were robbed of their personal possessions, often under the threat of violence.

Reports of the attacks started in February 2008, since when around 140 robberies are believed to have taken place, in a triangle between Agde, Orange and Fréjus.

The investigation culminated this month when around 500 gendarmes and police rounded up the gang members in Marseilles, Avignon and Toulon. All are believed to originate from the Balkans and are of Serbian or Croatian nationality.

The police seized around €100,000 in cash, as well as arms, and a not inconsiderable quantity of drugs.

Although most of those apprehended were unemployed, the police also took away a number of luxury German cars belonging to the gang.

Roland Gilles, Director General of the French Gendarmerie National, stated that the operation was "the result of a year-long investigation so that we can stop the actions of organised criminal gangs from the Balkans."

The incidents that have occurred on the French motorways are similar to robberies that have taken place in Spain.

In these cases the gangs punctured the tyres of their victims while they were at a motorway service station and then followed them until they were obliged to stop and change their tyre. When they stopped to offer assistance they would pounce.

Most of the victims were expats either returning to their homes in Spain or travelling over for a holiday.

Last year Spanish authorities broke up one of the gangs, arresting 19 people.