The rioters threw firebombs at two churches and attacked three schools on Sunday night, police said, hours after President Jacques Chirac vowed to defeat the troublemakers.
The new violence prompted warnings that the unrest which began on October 27 could damage investment and tourism in France and fuelled calls for the conservative government to take tougher action, including sending the army into riot-hit areas.
"This is real, serious violence. It's not like the previous nights. I am very concerned because this is mounting," said Bernard Franio, head of police for the Essonne area south of Paris, after about 200 youths attacked his colleagues in Grigny.
One of France's Muslim organisations, reacting to official suggestions that Islamist militants might be orchestrating some of the protests, issued a fatwa against the unrest but violence hit a new level overnight.
In the most serious incident, youths at a housing estate in Grigny, south of Paris, ambushed police with rocks, petrol bombs and guns.
Thirty-six police were hurt in the latest clashes, including two who were seriously wounded after being hit by shotgun pellets fired at them in Grigny.
A policeman at the scene held up a shotgun cartridge for cameras. Rioters fired live rounds at police and fire crews on Wednesday night, but no injuries were reported.
"There were burnt cars all over the place and helicopters circling overhead," said Yvonne Roland, who has lived in Grigny for 25 years. "Burning cars make a big impression, the flames were really high. It made you feel like you were in a war zone."
FIRST DEATH: The first fatality in the 11 days of violence was Jean-Jacques Le Chenadec, who died after being beaten on Friday in the northern Paris suburb of Stains, hospital officials and an Interior Ministry spokesman said.
The newspaper Le Parisien said the victim was 60 and had been in a coma since he was beaten outside his home on Friday.
Police said 1,408 vehicles were set ablaze and 395 people arrested overnight. The provincial cities of Marseille, Saint-Etienne, Toulouse, Metz and Lille were the worst affected.
The government has struggled to shape a response that could halt the riots, sparked by frustration among ethnic minorities over racism, unemployment and harsh treatment by police.
The United States has warned citizens to avoid areas hit by unrest and other countries have urged visitors to show caution. There have been some acts of arson abroad, including cars set on fire in Brussels and Berlin, but riots have not spread there.
The Action Police CFTC union urged the French government to impose a curfew on riot-hit areas and call in the army to control the youths - poor whites as well as French-born citizens of Arab or African origin complaining of racism.
"Nothing seems to be able to stop the civil war that spreads a bit more every day across the whole country," the CFTC said in a statement. "The events we're living through now are without precedent since the end of the Second World War."
CURFEW DECLARED: The mayor of Raincy, east of Paris, declared a night curfew for unaccompanied youths under the age of 18, the first such act since the unrest began with the accidental electrocution of two youths fleeing police outside Paris.
Far-right leader Jean-Marie Le Pen said there was a danger of civil war. Michel Pajon, Socialist mayor of Noisy-le-Grand north of Paris, demanded army intervention in riot-hit areas.
But national police chief Michel Gaudin refused to be drawn into comparisons between this surge of violence and protests that shook France in 19q68.
The head of France's main employers' group expressed concern about the impact the unrest could have on tourism and investment in France, where sluggish growth is stifling job creation.
"France's image has been deeply damaged," Laurence Parisot told Europe 1 radio.
Interior Minister Nicolas Sarkozy's tough line has been widely criticised but demands by Chirac that order be restored before any other measures are taken appeared to endorse him.
Police said youths torched a bus in Saint-Etienne in central France, injuring the driver and a passenger, and that rioters threw petrol bombs into a primary school in the eastern city of Strasbourg. Two other schools were also attacked, police said.
At Lens in the north and Sete in the south, firebombs were thrown at churches, he said.