Police said more than 40 vehicles were torched in the worst-hit northeastern region of Seine-Saint-Denis, where 1,300 officers were deployed, and more than 30 people were arrested there and elsewhere.
Shots were also fired at riot police vans without causing injury.
A top government official for the region, Jean-Francois Cordet, said the violence was “spreading to the east and north” of Seine-Saint-Denis with only a few areas with a heavy police presence remaining “relatively calm.”
Five officers were hurt by projectiles thrown by youths in the western suburb of Mantes-La-Jolie.
And for the first time since the troubles first erupted on Thursday of last week, there were sporadic signs of copycat rampages elsewhere in France.
Police said several cars in the eastern city of Dijon were set alight.
French Prime Minister Dominique de Villepin has vowed his government “will not give in” to the rioters.
“I will not allow organised gangs to make the law in the suburbs,” he declared in parliament.
Interior Minister Nicolas Sarkozy, whose hardline law-and-order policies have been blamed for fanning the acts of defiance, said 143 people have so far been arrested in the clashes.
Mr Sarkozy said the street violence “was not spontaneous, it was perfectly organised, we are looking into by whom and how.”
The interior minister, who harbours presidential ambitions, last month promised to wage a “war without mercy” on youth crime.
Some of the youths taking part in the troubles have responded by pledging to continue the “war” against the police “until Sarkozy resigns.”
Mr Villepin, who cancelled a trip to Canada to tackle the crisis, called the violence “unacceptable” and said restoring order was the government’s “absolute top priority.”
President Jacques Chirac has called for calm, warning that an escalation would be “dangerous”.
An interim report of an investigation into the electrocution deaths of two teenage boys that set off the rioting appears to exonerate police.
But the families of the two teenagers and a third who was seriously injured have filed a legal complaint for “failure to assist a person in danger,” a crime in France, their lawyer, Jean-Pierre Mignard, said.
The complaint, filed on Tuesday, does not target specific individuals.
The drama unfolded as several boys trespassed on a building site after playing soccer, the report released by the Interior Ministry said.
Many youths in Clichy-sous-Bois, north east of Paris, believe that police chased the victims – Bouna Traore, 15, born in Mauritania, and Zyed Benna, 17, of Tunisian origin – to their deaths last week.
The incident has sparked what is now nightly unrest across the entire region of Seine-Saint-Denis.
The area is dotted with low-income suburbs made up of housing projects which are home to large migrant and predominantly Muslim communities.
Up to 20 suburbs have been affected by the unrest, with hundreds of cars and buildings set ablaze.
Hiding from police
The report says that 11 police officers called to the scene detained six people and had returned to their post 22 minutes before the deadly incident at a power substation owned by the electricity company EDF.
The report quotes a third young man who was badly injured, Muttin Altun, 17, of Turkish descent, as saying the boys knew of the dangers of hiding out in the power substation, but did so thinking they were being pursued by police.
The report, citing Altun’s account, said that after a group of boys had finished playing football, several of them entered a building site.
The three in question fled when police arrived, crossing a wooded area.
They then scrambled into the power substation to hide.
Altun “did not see the exact circumstances of the accident, having lost consciousness immediately,” the report said. Altun remained hospitalised, Mr Mignard said.
“We want the truth to come out,” Amor Benna, father of Zyed Benna, said in a telephone interview.
He said that neither he nor the other families was seeking personal gain by filing a complaint.
“Money will not bring back my son,” he said. “We want to know if a mistake was made by security (police) or not.”
Separate administrative and judicial investigations into the deaths were also underway.
For sociologists and many commentators in France, the riots have laid bare the failure of successive government’s policies in addressing the grim existence of those living in run-down public housing estates, some of them little more than ghettos where crime and gangs run rampant.
The country has 751 neighbourhoods officially classed as severely disadvantaged, housing a total of five million people, around eight percent of the population.
Conditions are often dire with high-rise housing, unemployment at twice the national rate of 10 percent and per capita incomes 40 percent below the national average.
Many of France’s estimated five million Muslims live in those suburbs, and authorities were left wondering whether the end overnight Thursday of the Islamic holy month of Ramadan would bring more or less violence.