French Prime Minister Dominique de Villepin has promised to stiffen punishments for vandals after youths torched a bus in the southern city of Marseille, leaving a badly burned woman fighting for her life.
With the weekend attack coming exactly one year after the start of widespread riots in poor, largely immigrant French suburbs, the conservative government sought to quell fears that France risked a new wave of unrest.
"Faced with such violent acts, the first response must be the systematic arrest of all those involved and their exemplary and speedy punishment," Villepin said after a special meeting with ministers on public transport security.
"We will not only punish those directly responsible for an ambush, as has been the case before, but also those who take part in or encourage them," the prime minister said.
The Marseille attack followed the torching of several buses and cars around Paris in recent weeks. Police had warned that a wave of violence ahead of the anniversary of last year's events risked spiraling out of control.
But Interior Minister Nicolas Sarkozy said he saw no risk of violence spreading despite the weekend attack, urging his compatriots not to play up the riot anniversary date.
"Some people have kept putting oil on the fire by talking about the commemoration of an anniversary that isn't one. But contrary to their hopes, there's no risk of contagion for the moment," he told Europe 1radio.
Sarkozy said officials were close to identifying the hooded vandals who held up the Marseille bus on Saturday evening and torched it before student Mama Galledou could escape. The 26-year old suffered burns to 60 percent of her body.
Sarkozy, who is loved and loathed in equal measure for his tough talk on law and order, has faced criticism from opposition leftists for continuing violence in France's rundown suburbs.