Marauding bands of Muslim youth set fire to cars and warehouses and pelted rescuers with rocks early Saturday, as the worst rioting in a decade spread from Paris to other French cities. The United States warned Americans against taking trains to the airport via strife-torn areas.

A savage assault on a bus passenger highlighted the dangers of travel in Paris' Muslim-filled and impoverished outlying neighborhoods, where the violence has entered its second week.

The African immigrant attackers doused the woman, in her 50s and on crutches, with an inflammable liquid and set her afire as she tried to get off a bus in the suburb of Sevran (search) Wednesday, judicial officials said. The bus had been forced to stop because of burning objects in its path. She was rescued by the driver and hospitalized with severe burns.

Justice Minister Pascal Clement (search) deplored the incident, saying it caused him "great emotion."

Rioters burned more than 500 vehicles Friday as the unrest grew beyond the French capital for the first time. Unrest returned to the streets in the evening and early Saturday, the ninth night in a row.

Police said troublemakers fired bullets into a vandalized bus and burned 85 more cars in Paris and Suresnes, just to the west. In Meaux (search), east of Paris, officials said youths stoned rescuers aiding someone who had fallen ill.

Meanwhile, warehouses in Suresnes and Aubervilliers, on the northern edge of Paris, were set ablaze. Officials said other fires raged outside the capital in Lille, Toulouse, and Rouen, while an incendiary device was tossed at the wall outside a synagogue in Pierrefitte, northwest of Paris.

Some 30 mayors from the Seine-Saint-Denis region (search) where the unrest started Oct. 27 met Friday to make a joint call for calm. Claude Pernes, mayor of Rosny-sous-Bois, denounced a "veritable guerrilla situation, urban insurrection" that has taken hold.

A national police spokesman, Patrick Hamon, said there appeared to be no coordination among gangs in different areas. But he said youths in individual neighborhoods were communicating by cell phone text messages or e-mails — arranging meetings and warning each other about police operations.

The violence started Oct. 27 after the accidental electrocution of two teenagers who believed police were chasing them in the Seine-Saint-Denis region, dominated by low-income housing projects.

Since then riots have swelled into a broader challenge against the French state and its security forces. The violence has exposed deep discontent in neighborhoods where African and Muslim immigrants and their French-born children are trapped by poverty, unemployment, racial discrimination, crime, poor education and housing.

During the day Friday, the burned remains of at least 520 cars littered Parisian streets, an increase from previous nights. Five police officers were lightly injured by youths throwing stones or bottles, the Interior Ministry said.

At a depot in Trappes, to the southwest, 27 buses were incinerated, officials said.

The commuter train line linking Paris to Charles de Gaulle (search) airport ran limited service Friday after two trains were targeted Wednesday night.

The U.S. Embassy (search) called the protests "extremely violent" and warned travelers against taking trains to the airport because they pass through the troubled area. Russia, meanwhile, warned citizens against visiting the suburbs.

The Foreign Ministry said it was concerned that foreign media coverage was exaggerating the situation. "I don't have the feeling that foreign tourists in Paris are in any way placed in danger by these events," ministry spokesman Jean-Baptiste Mattei said, adding that officials were "sometimes a bit surprised" by the foreign coverage.

Still, the violence has alarmed the government of President Jacques Chirac (search), whose calls for calm have gone unheeded.

"This is the first time (suburban violence) has lasted so long and the government appears taken aback at the magnitude," said Pascal Perrineau, director of the Center for Study of French Political Life.

There were "few direct clashes" with security forces late Thursday and early Friday, however, no bullets fired at police, and far fewer large groups of rioters, said Jean-Francois Cordet, the top government official in Seine-Saint-Denis.

Instead, Cordet said, the unrest in Seine-Saint-Denis was led by "numerous small and highly mobile groups" that burned 187 vehicles and five buildings, including three warehouses.

The unrest erupted with youths angered over the deaths of Bouna Traore, 15, and Zyed Benna, 17, who were electrocuted when they hid in a power substation in the suburb of Clichy-sous-Bois.

Traore's brother, Siyakah Traore, called for protesters to "calm down and stop ransacking everything."

"This is not how we are going to have our voices heard," he told RTL radio, adding his voice to neighborhood groups working to stop the violence.

Dozens of residents and community leaders were stepping in to defuse tensions, with some walking between rioters and police to urge youths to back down.

Abderrhamane Bouhout, head of the Bilal mosque in Clichy-sous-Bois (search), said he had enlisted 50 youths to try stop the violence. "We've had positive results," he said.