A senior police union official warned that "urban guerrillas" had joined the unrest, saying the violence has been worse than during three weeks of rioting that raged across French cities in 2005, when firearms were rarely used.
Two dozen people have been detained so far and some 120 police officers have been injured, four of them seriously after being hit by buckshot from hunting weapons, police say.
Douhane Mohamed of the Synergie police union said two things were cause for anxiety: "Signs the violence is spreading to neighbouring areas, which have already had their share of burned cars, and the almost systematic use of firearms against police."
Bands of youths – some as young as 13 – set more cars and garbage bins on fire on Tuesday in and around Villiers-le-Bel, the Paris suburb where the latest trouble first erupted, and a grocery store was torched in a nearby town.
In the south, 10 cars and a library were torched in Toulouse, police said.
The unrest highlighted smouldering resentment in France's poor neighbourhoods, where many Arabs, blacks and other minorities live largely isolated from the rest of society – the same neighbourhoods at the heart of the 2005 riots.
The trigger this time was the deaths on Sunday of two teenagers from ethnic minorities in a motorcycle crash with a police car in Villiers-le-Bel, a blue-collar town in Paris' northern suburbs.
Relatives of the two youths and some local residents said police had caused the accident and fled the scene without treating the victims but an initial investigation found the two teenagers - neither wearing crash helmets - careered into the police car.
Officials said police stayed on the scene until firefighters arrived.
|The PM has vowed to boost security and "do |
everything" to stop violence spreading [AFP]
Rioting and arson quickly erupted after the crash, and it spread on Monday from Villiers-le-Bel to other towns north of Paris.
Some 200 people staged a silent march late on Tuesday in Villiers le Bel in the youths' memory but police union officials said officers have been confronted by violence more intense than during the 2005 riots.
Youths, many of them Arab and black children of immigrants, again appeared to be lashing out at police and other targets seen to represent a French establishment they feel has left them behind.
Gilles Wiart of the SGP-FO police union said he did not think it was an "ethnic problem".
"Most of all it is youths who reject all state authority. They attack firefighters, everything that represents the state."
Nicolas Sarkozy, the French president, appealed for calm from China where he was on a visit, and called a security meeting with his ministers on Wednesday on his return home.
Sarkozy was interior minister in charge of police during the riots of 2005 and was accused of adding fuel to fire when he called the youth "scum".
Linda Beddar, a 40-year-old mother of three in Villiers-le-Bel, said the youth "want Sarkozy. They want him to come and explain" what happened to the two teenagers.