They have lived largely unnoticed for years, isolated from the French mainstream by language and religion. Now these imams, accused of preaching a radical brand of Islam, are being tracked, investigated and in some cases expelled.
Taking the lead in a budding get-tough trend among some European governments, France has expelled at least two imams, or prayer leaders, since January, calling them a public danger. It is threatening to expel two more, and a fifth is under arrest.
Critics say the aggressive policy could do more harm than good, but France isn't alone. Italy deported an imam from Senegal in November, deeming him a "danger to state security." He had warned that Italian soldiers in Iraq and Afghanistan risked attack. Days later 19 Italians in Iraq were killed.
Britain jailed an imam from Jamaica for nine years in March 2003 for urging followers to kill Hindus, Jews and Americans. It is now trying to deport another high-profile cleric, Abu Hamza al-Masri, accusing him of advising and supporting terrorist groups, including al-Qaida.
Spain, where 191 people died in the March 11 railroad bombings, is considering a law empowering authorities to monitor imams.
But France has set a policy of actively going after imams whose discourse veers into a defense of violence or espouses values counter to democracy or human rights.
Radical imams "are a natural bridge toward violence, that is, toward terrorism," said Stephane Berthomet, a former anti-terrorism investigator with the Interior Ministry. They also are a "social danger," he said, because "they reject the French system."
But it's not so simple. European civil rights laws don't always lend themselves to swift expulsion, as Britain has learned in dealing with al-Masri. It revoked his citizenship five months ago, calling him a threat to the country's interests, but he appealed to a special immigration tribunal and a ruling is likely to take months.
Abdelkader Bouziane, one of two imams expelled from France last month, quickly won a court ruling allowing him to return.
The Algerian, who has 16 children from two wives, advocated violence in his sermons, the Interior Ministry said. French media had quoted him as saying he favors wife-beating and stoning of women.
On Saturday, police detained a Turkish imam at a Paris mosque who allegedly headed an extremist movement that advocates violence and terrorism. Midhat Guler, 45, immediately applied for political asylum.
Guler has lived in France for 28 years and has five children. He has directed the mosque since 1984, his son, Abdurrahman Guler, told French television.
Lhaj Thami Breze, president of the powerful Union of Islamic Organizations of France, which is considered close to Egypt's Muslim Brotherhood, said the expulsions are excessive and the fanfare is unwise.
"This feeds the fear in the Muslim community that it, once again, is being singled out," Breze said in a telephone interview. "It gives the impression that France is persecuting Muslims."
On the other hand, the rector of the Paris Mosque approved.
"We have to work hand in hand ... so that the function of the imam, the status of the imam in France, is above any suspicion," Dalil Boubakeur said Monday.
France, whose Muslim community of 5 million is western Europe's largest, wants an "Islam of France" to emerge that reflects the country's values.
The concern has been heightened by a growing realization that a generation of poor, marginalized Muslim youths is growing up alienated from French mainstream society and schooling. These youths are widely blamed for a wave of anti-Semitic violence in France.
The imams themselves reflect the problem of alienation. Most of the 1,500 in France come from abroad and fewer than half speak French.
The isolation of Muslim youths makes them particularly vulnerable to radical preachings, said Berthomet, the former anti-terrorism officer.
"These radicals penetrate some suburbs more easily than social workers or police," he said.