Last updated at 20:03 27 November 2007

Nicolas Sarkozy yesterday flew home early from a trip to China to attend crisis talks over the "urban warfare" erupting in Paris.

Emergency security measures were imposed after armed gangs turned the streets of the French capital into a battleground.

The violence, which has spread to six towns north of Paris, began after two teenagers died when their motorbike collided with a police car in a suburb on Sunday.

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Protesters claimed that the officers involved left the scene without helping the injured youths.

The French president will arrive home tomorrow two days ahead of schedule for urgent talks with his senior ministers.

More than 80 police officers have been injured in the running battles with gangs of hooded youths.

In a second day of violence yesterday, the riots took a dramatic and potentially deadly new turn with the use of firearms against police.

Patrice Ribeiro, a senior police union official, said the violence overnight Monday to Tuesday was more intense than during three weeks of rioting in 2005.

He said "genuine urban guerillas with conventional weapons and hunting weapons" were among the rioters.

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The use of firearms added a dangerous new dimension. Guns were rarely used in the 2005 riots that spread to poor housing projects nationwide.

Police are facing "a situation that is far worse than that of 2005," said Ribeiro, national secretary of the Synergie officers union.

"Our colleagues will not allow themselves to be fired upon indefinitely without responding," he warned on RTL radio.

"They will be placed in situations which will become untenable."

Worst hit was Villiers-le-Bel, north of the capital, where two teenagers died when their motorbike collided with a police car on Sunday night.

Omar Sehhouli, brother of one of the victims, accused police of ramming the motorbike and of failing to assist the victims.

The public prosecutor is investigating the officers involved for manslaughter and leaving the scene of an accident but it did nothing to appease the mobs who took to the streets for a second night.

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The officers were attacked with missiles including metal bars and Molotov cocktails.

Riot squads hit back with rubber bullets, tear gas, and paint canisters designed to identify troublemakers.

President Sarkozy has appealed to "all sides to calm down and for the judiciary to decide who bears responsibility".

But there are fears of a repeat of the nationwide riots that led to a state of emergency being declared in autumn 2005.

Then the trouble was started by the deaths of two young men in an electricity substation as they tried to flee police in the Paris suburb of Clichysous-Bois.

Dozens of vehicles were set on fire yesterday in the Val d'Oise district, including a bus.

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About a dozen people forced the driver out of the bus before beating him up, said local police.

In Villiers-le-Bel, a pre-school, a library, a driving school and a beauty salon were destroyed by fire.

"It's a hugely dangerous situation," said one officer. "It appears that these youths want to kill us."

Some youths tried to pull down cables leading to street lamps in a bid to black out the area.

Police and politicians warn the French suburbs remain a "tinderbox".

"These neighbourhoods live in a state of permanent depression, but all it takes is one drop to make the depression boil over into anger," said sociologist Laurent Mucchielli.