On Saturday Interior Minister Nicolas Sarkozy called a meeting of police chiefs to discuss tactics as they braced for another night of violence that has so far defied all efforts to stamp it out.
In a sign of the government's resolve, police said more than 250 people were arrested on Friday night alone - doubling the number of detentions recorded since the troubles first erupted on 27 October.
Nearly 900 vehicles were torched that same night, making it the worst in terms of the arson attacks that have come to characterise the rampages.
Prime Minister Dominique de Villepin held a crisis meeting with Sarkozy and other key ministers on Saturday, as the rioting dominated world headlines and prompted the United States and Russia to warn its citizens against travelling through Paris suburbs.
Officials were "unanimous in their firmness" in seeking an end to the violence, Sarkozy said after the meeting.
"The violence is not acceptable," he told journalists.
Grim suburb conditions
While the government acknowledged that the grim conditions in the suburbs - chronic high unemployment, racial discrimination, miserable housing, drugs - had much to do with the discontent, Sarkozy and other security officials also voiced suspicions that the unrest was being organised.
Paris prosecutor general Yves Bot told Europe 1 radio on Saturday there was "organised violence," but did not say by whom.
Many residents have been forced
from their homes by arson
"If I could give an exact answer, those people would already be under arrest," he said. "But we can see organised actions, a strategy."
Youths have been seen relaying police movements by mobile telephone, and have started internet weblogs urging other parts of France to join the unrest.
While deprived suburbs with large immigrant Arab and African populations on the fringes of Paris were again the scene of the worst of the riots, violence has also flared in other cities around the country - Lille, Rouen, Rennes, Toulouse, Marseille - over the past two nights.
The prospect of coordinated actions is of special concern in France, given that the areas most affected by the violence are downtrodden suburbs with high concentrations of Muslims.
The country is home to Europe's biggest Muslim community, estimated at more than five million, or nearly 10% of the population.
No religious dimension
So far, though, there has been no religious dimension given to the riots. Those taking part have spoken more of protesting against the misery of their lives in the fringe towns, where unemployment of more than 20% is the norm.
The violence began last week when two teenagers, of African and Arab origins, were electrocuted while hiding in an electrical sub-station after fleeing a police identity check.
Violence has spread from Lille in
the north to Marseille in the south
Since then, there has been evidence it has been fanned by tough rhetoric by Sarkozy, who has been preparing a bid to run in 2007 presidential elections on the strength of "zero tolerance" law-and-order policies.
Most contentious was his choice of language just before the rioting, when he called delinquents "rabble" and vowed to clean their districts "with a power-hose".
"It was calm for a long time here. If there hadn't been Sarko's words - 'power-hose,' 'rabble' - there wouldn't have been all this," a 22-year-old man in the northern tinderbox suburb of Aulnay-sous-Bois said.
"He makes us suffer, he's a racist. He's put fuel on the fire," Fatou, a 14-year-old boy of African background, said.
An imam at a Paris mosque, Dalil Boubakeur, said after meeting Villepin on Saturday that Sarkozy and other politicians should be using "words of peace," adding that "in such difficult circumstances, each word is important".
Although car-burning and rioting has been a regular, if little-reported fact of life in France's tough neighbourhoods over the past 15 years, the duration, intensity and reach of the latest violence has been unprecedented since 1968 student revolts.
In total, since the beginning of the rioting, more than 2000 vehicles have been burnt and around 500 people arrested.
"He makes us suffer, he's a racist. He's put fuel on the fire"
14-year-old boy of African origin
A few shots have been fired at police - an unusual occurrence in France - but did not cause any injuries.
There have been no deaths so far, but at least two people have been badly burnt by Molotov cocktails: a fireman, and a handicapped woman unable to get off an ambushed bus.
A 61-year-old was also in a coma after being beaten in a public housing estate.