There are no minarets at the Bilal Mosque. Hidden out of sight behind a shopping center, it looks more like a warehouse than a house of prayer, with cinderblock-and-plaster walls covered with faded green Arabic lettering.

It was here that police launched a tear gas grenade whose fumes filled the mosque at prayer time — inflaming passions as riots engulfed derelict, mostly immigrant neighborhoods across France.

Almost no one believes radical Islam was a trigger for the rioting that began three weeks ago. But experts and authorities fear the social discontent that found an outlet in the rampaging could evolve among a small minority of the rioters into a dangerous form of Islamic militancy.

Many predict the months to come will become a struggle for the soul of these angry communities — with the authorities, Islamic radicals, drug gangs and social welfare groups all vying for influence among troubled youths.

"We will see recruitment opportunities for jihadists because some youths who participated in the riots are going to say 'What's the use of burning cars? ... We have to go on to a higher level,"' said Olivier Roy, one of Europe's most prominent scholars of Islamic society.

"Those people will either turn toward terrorism in France or go to places like Fallujah," the one-time insurgent stronghold in Iraq.

French Interior Minister Nicolas Sarkozy — whose aggressive handling of the riots has been applauded by much of France, even as his tough talk against rioters generated resentment in poor housing projects — singled out two enemies in his battle to regain control of largely immigrant neighborhoods.

"The hour of truth has come," Sarkozy told the Senate this week. "We must not let the rule of the gangs and the rule of the bearded ones prevail!" — referring, in typically brash fashion, to radical imams by their facial hair.

French counterterrorism chief Pierre de Bousquet used more measured language, but his message was just as stern.

"Among the most fiery of these youths, some may find for their disquiet, their frustrations, their violence ... an outlet in international jihad," Bousquet said in an interview with Valeurs Actuel magazine. "The situation is very worrying and the threat is high."

The head of the Bilal Mosque, Abderrahman Bouhout, played down the risk of Islamic militancy, saying jihadist anger would have exploded immediately after the tear gas incident if such sentiments had taken root. "After the mosque was gassed, I felt hatred ... I felt anger," he said. "But then things calmed down."

However, Lucienne Bui Trong, former chief of France's urban violence intelligence unit, said anti-Western sentiment has been growing — and that the atmosphere created by the riots provides fertile ground for terrorism.

Bui Trong said there is a familiar pattern of young people starting off in petty crime and drugs, then turning as adults to an extreme form of Islam.

"We have seen a ... rise for several years of animosity directed at France," she said.

Bui Trong warned of a dangerous cocktail in poor neighborhoods. The growing insularity of immigrant communities, resentment against society and the opportunity for recruitment by Islamists have created, "an ideal terrain for terrorism," she said.

Experts say the terror threat remains strong even though France opposed the war in Iraq, because anger among Islamists here is directed at Western society and many Muslims were deeply offended by France's ban on head scarves in public schools.

The Islamists, said Bui Trong, "work on minds unyieldingly in the direction of demonizing Western society."

Sebastian Roche, a security expert at the state-funded National Center for Scientific Research, said the terror threat in the suburbs may grow if the economic situation becomes more desperate.

But he drew distinctions between the profile of rioters and that of international terrorists.

"Those who participated in the riots are not political militants, they are not religious militants. Their profile is typical of street delinquents — young, poorly educated, they commit acts that do not benefit their cause, if they have a cause," he said.

"Terrorists generally are people with higher education, who have been to university, and who want to sacrifice themselves for a cause."

However, Roy saw parallels between the discontent among the rioters and the British-born perpetrators of the London transit bombings in July. The bombers grew up adopting largely secular ways, became embittered, then were lured by Islamic militancy. Roy fears youths in Paris housing projects could follow the same path.

"Those who carried out the London bombings exist in Paris, they exist in Stockholm, they exist everywhere," he said. "We have an environment that can swing into jihadism or stay within delinquency."

"The police estimate there were about 20,000 participants across France in the riots, so if you have 1 percent of the 20,000 who become radicalized that's 200," he said. "In sociological terms it's negligible, but in terms of impact — 200 jihadists, yes, that counts."

Experts say a sweeping reform of the police force is needed for authorities to make lasting inroads in reducing both the terror threat and crime in poor neighborhoods.

The police have been criticized for rough tactics — using racial slurs, demanding identification cards indiscriminately, slamming minority youths against the wall for no reason.

But an equally troubling problem appears to be a deep ignorance of their beat. The tear gas incident at Bilal Mosque may have occurred simply because police didn't realize it was a place of worship.

Roy said: "The French police are an excellent police of repression ... but they are very bad in prevention."

"We need to form a whole new police corps," he said. "It needs to recruit many people from the suburbs."