Six hundred extra police have been sent to the poorer areas of Strasbourg, in eastern France, in an attempt to stop what has become an annual seasonal car-burning festival.
Since Christmas about 40 vehicles, including a tram, have been set on fire by gangs of young people determined to push vandalism beyond record levels.
Last year the Socialist-run city, which wants to become Europe's capital, recorded 570 car fires, most during summer and winter school holidays.
With the Christmas flare-up, the number of gutted vehicles has reached nearly 700 this year, and the authorities are preparing for a repeat of last year's exceptionally hot New Year's Eve, when 136 vehicles were set ablaze.
Although the city on the German border has a bourgeois image as the seat of the European Parliament and the Council of Europe, 40 per cent of the population lives in poor, high-rise areas, heavily populated by north African and Turkish immigrants.
But sociologists believe the car burning has no direct connection with high unemployment or racist tension.
Fatah Boudjelida, president of a youth association in the poor suburb of Cronenbourg, said the vandalism was committed by children aged 14 to 16 who were not considered rebellious.
'They can be very nice during the day but as soon as night falls they set alight to vehicles for no apparent motive,' the youth leader said, adding that most of the cars had been parked in poor suburbs.
'They want to set a record so they'll be spoken about. Some see it as a sporting occasion.' A dozen young people have been arrested this week for car thefts or more serious vandalism, including trying to burn down a school. Local councillors are at a loss how to stop the rioting.
The city council set aside £400,000 for the Christmas week to sponsor dozens of cheap pop concerts, discos and other entertainment to lure young people off the streets. Although well attended, the events failed to distract the car burners.
'A similar entertainment operation was tried during the summer holidays and that achieved its purpose.' the city's spokesman, Jean-Francois Lanneluc, said.
'There must be a way of getting the same result in winter but we don't know how.' Stung by demands from the rightwing opposition for a tougher clampdown, the assistant mayor, Alain Kauff, said law and order operations would only provoke further violence.
'For many young people, car burning is just a perverse game,' he said.
'They meet up to satisfy media pressure for spectacular news images. It's a vicious circle.'