French authorities had deployed 1,000 policemen to counter rioters, but struggled to contain youths who hurled petrol bombs and bricks, shot at officers and burned cars and buildings.
Sarkozy's remarks came after a hospital visit on Wednesday to see one policeman critically injured in the first night of rioting in Villiers-le-Bel.
He said that the offence "has a name, it is attempted murder. Opening fire at officials is completely unacceptable ... we will find the gunmen".
Having returned from a state visit to China, Sarkozy was due to have emergency talks with his ministers later on Wednesday.
The present rioting is the worst in the country since major riots erupted in 2005.
The president was the interior minister in charge of police during the 2005 riots and was accused of adding fuel to fire when he called the youth "scum".
Francois Fillon, the prime minister, has vowed to boost security and to "do everything" to stop the violence from spreading.
A senior police union official warned that "urban guerrillas" had joined the unrest, saying the violence has been worse than during three weeks of rioting in 2005, when firearms were rarely used.
Two dozen people have been detained so far and some 120 police officers have been injured, four of them seriously after being hit by buckshot from hunting weapons, police say.
Douhane Mohamed of the Synergie police union said two things were cause for anxiety: "Signs the violence is spreading to neighbouring areas, which have already had their share of burned cars, and the almost systematic use of firearms against police."
Bands of youths – some as young as 13 – set more cars and garbage bins on fire on Tuesday in and around Villiers-le-Bel, and a grocery store was torched in a nearby town.
The unrest highlighted smouldering resentment in France's poor neighbourhoods, where many Arabs, blacks and other minorities live largely isolated from the rest of society – the same neighbourhoods at the heart of the 2005 riots.
Relatives of the two youths who died in Villiers-le-Bel and some local residents said police had caused the accident and fled the scene without treating the victims but an initial investigation found the two teenagers - neither wearing crash helmets - had careered into the police car.
Officials said police stayed on the scene until firefighters arrived.
|The authorities have deployed about 1,000 |
policemen to curb the violence[AFP]
Rioting and arson quickly erupted after the crash, and it spread on Monday from Villiers-le-Bel to other towns north of Paris.
Some 200 people staged a silent march late on Tuesday in the town in the youths' memory.
Youths, many of them Arab, and children of black immigrants, again appeared to be lashing out at police and other targets seen to represent a French establishment they feel has left them behind.
Gilles Wiart of the SGP-FO police union said he did not think it was an "ethnic problem".
"Most of all it is youths who reject all state authority. They attack firefighters, everything that represents the state."