On a routine call, three unwitting police officers fell into a trap. A car darted out to block their path, and dozens of hooded youths surged out of the darkness to attack them with stones, bats and tear gas before fleeing. One officer was hospitalized.

The recent ambush was emblematic of what some officers say has become a near-perpetual and increasingly violent conflict between police and gangs in tough, largely immigrant French neighborhoods that were the scene of a three-week paroxysm of rioting last year.

One small police union claims officers are facing a "permanent intifada." Police injuries have risen in the year since the wave of violence.

National police reported 2,458 cases of violence against officers in the first six months of the year, on pace to top the 4,246 cases recorded for all of 2005 and the 3,842 in 2004. Firefighters and rescue workers have also been targeted — and some now receive police escorts in such areas.

On Sunday, a band of about 30 youths, some wearing masks, forced passengers out of a bus in a southern Paris suburb in broad daylight Sunday, set it on fire, then stoned firefighters who came to the rescue, police said. No one was injured. Two people were arrested, one of them a 13-year-old, according to LCI television.

More broadly, worsening violence in France testifies to Europe's growing struggle to integrate its ethnic minorities. Some mainstream European politicians — adopting positions previously confined largely to far-right fringes — are suggesting that the minorities themselves are not doing enough to adapt to European mores.

In Britain, former Foreign Minister Jack Straw, now leader of the House of Commons, this month touched off a wide debate about the rights and obligations of Muslims by saying that he asks devout Muslim women to remove their veils when visiting his office. Prime Minister Tony Blair said Islam needs to modernize.

In France, a high school teacher received death threats, forcing him into hiding, after he wrote a newspaper editorial in September saying Muslim fundamentalists are trying to muzzle Europe's democratic liberties.

Ethnic integration and violence against police are both becoming issues in the campaign for the French presidency. Interior Minister Nicolas Sarkozy, the leading contender on the right, said this month that those who do not love France do not have to stay, echoing a longtime slogan of the extreme-right National Front: "France, love it or leave it."

Michel Thooris, head of the small Action Police union, claims that the new violence is taking on an Islamic fundamentalist tinge.

"Many youths, many arsonists, many vandals behind the violence do it to cries of 'Allah Akbar' (God is Great) when our police cars are stoned," he said in an interview.

Larger, more mainstream police unions sharply disagree that the suburban unrest has any religious basis. However, they do say that some youth gangs no longer seem content to throw stones or torch cars and instead appear determined to hurt police officers — or worse.

"First, it was a rock here or there. Then it was rocks by the dozen. Now, they're leading operations of an almost military sort to trap us," said Loic Lecouplier, a police union official in the Seine-Saint-Denis region north of Paris. "These are acts of war."

Sadio Sylla, an unemployed mother of three, watched the Oct. 13 ambush of the police patrol in Epinay-sur-Seine from her second-floor window. She, other witnesses and police union officials said up to 50 masked youths dashed out from behind trees.

One of the three officers needed 30 stitches to his face after being struck by a rock. On Saturday, five people were placed under investigation for attempted murder in relation to the ambush.

The attack was one of at least four gang beatings of police in Parisian suburbs since Sept. 19. Early Friday, a dozen hooded people hurled stones, iron bars and bottles filled with gasoline at two police vehicles in Aulnay-sous-Bois, a flashpoint of last year's riots, said Guillaume Godet, a city hall spokesman. One officer required three stitches to his head.

Minority youths have long complained that police are more heavy-handed in their dealings with them than with whites, demanding their papers and frisking them for no apparent reason.

Such perceived ill-treatment fuels feelings of injustice, as do the difficulties that many youths from immigrant families have finding work.

Distrust and tension thrive. Rumors have flown around some housing projects that police are hoping to use the Muslim holy month of Ramadan, which ends this week, to round up known troublemakers, on the basis that fasting all day will have made the youths weaker and easier to catch.

Police say that suggestion is ludicrous. However, they are on guard ahead of the first anniversary this week of last year's riots. That violence began after two youths who thought police were chasing them hid in a power substation and were electrocuted to death.

Police unions suspect that the recent attacks may be an attempt to spark new riots.

"We are getting the impression these youths want a 'remake' of what happened last year," said Fred Lagache, national secretary of the Alliance police union. "The youths are trying to cause a police error to justify chaos."