A helicopter was deployed early on Tuesday over the town of Villiers-le-Bel, 20 kilometers (12 miles) north of the French capital "to locate people stirring up trouble," a police officer told the news agency AFP.

The violence broke out on Sunday night after two teenagers of African origin, aged 15 and 16, were killed when their motorcycle was struck by a police car.

French police union officials said that 77 officers were injured on Monday night and that several of them were in critical condition.

"One policeman was wounded in the shoulder after being hit by a high-caliber bullet," a security official said, adding that "no vital organ was affected."

Rampaging youths threw Molotov cocktails and set fire to dozens of trash cans and cars in the violence that spread to three other neighborhoods. Police in full riot gear responded with tear gas, rubber bullets and paint guns designed to mark the rabble-rousers.

Police investigation

State prosecutor Marie-Therese Givry ordered an internal police investigation for "involuntary manslaughter and failure to assist persons in danger" following the deaths of the two teenagers.

Speaking later to the media, she said witnesses had corroborated the police officers' account of the accident. Police claimed that the bike smashed into the side of their car during a routine patrol and that neither youth was wearing a helmet.

"I will not allow it to be said that police services did not help the youths," she said. "Help was summoned. Emergency services came straightaway. Everything was done to save them."

Police also said that the motorcycle was stolen and that the two youngsters ignored traffic regulations.

Police were accused of ramming the motorbike and of running away. "This is a failure to assist a person in danger," a witness told France Info radio. "It is 100-percent a [police] blunder. They know it, and that's why they did not stay at the scene."

Unresolved tensions

Villiers-le-Bel is a community of 27,000 people, many of them immigrants of Arabic or African origin. It is considered to be, like several other neighborhoods north of the French capital, a sensitive zone of unresolved social tensions.

The latest spurt of street violence revived memories of the three weeks of urban unrest that spread through poor suburbs throughout France in November 2005 after two teenagers were killed in an electricity sub-station while hiding from police.

After Sunday's night of violence, French President Nicolas Sarkozy appealed for calm.

Speaking on a trip to Beijing, Sarkozy called for "all sides to calm down and for the judiciary to decide who bears responsibility."