PARIS -- Jewish and Muslim leaders here warned on Monday of rising anti-Semitism among young Muslims, two days after the police arrested 11 men and fatally shot one in raids in a handful of cities aimed at young radical French Muslims.
President François Hollande met with Jewish and Muslim leaders on Sunday and promised tighter security at Jewish religious sites. He said that a new law would soon make it a crime to travel to militant training camps. "Nothing will be tolerated; nothing should happen," Mr. Hollande said in a statement. "Any act, any remark will be prosecuted with the greatest firmness."
News of the raids added to the anxieties of France's Jewish and Muslim populations, which were already unnerved by the killings in March of three French service members, a rabbi and three Jewish children in the Toulouse region by a French Muslim who had trained with Islamic militants in Pakistan. Muslim and Jewish spokesmen say they worry about the domestic expansion of radical Islam.
"We must take the measure of this type of ideology," Richard Prasquier, the head of Crif, a major Jewish organization in France, told France Inter radio on Monday. "I say that radical Islamism is Nazi ideology."
Dalil Boubakeur, the rector of the Grande Mosquée in Paris, also warned of radicalism, but said those arrested did not represent Muslims as a whole.
The raids took place near Paris and in Nice, Cannes and Strasbourg, where police officers killed Jérémie Louis-Sidney, 33, after he fired on them with a .357 Magnum pistol when they entered the apartment he was in. His DNA was found on the remnants of a small grenade that was thrown into the kosher market in Sarcelles, a suburb of Paris, last month. The police described him as a French-born drug dealer who had become radicalized in prison and converted to Islam there. They said he had been under surveillance for months.
On Monday, French newspapers similarly described the 11 suspects as young men born in France who had adopted a radical form of Islam, usually after coming into trouble with the law. An editorial in the daily newspaper Libération called them "the lost children of the lost territories of the republic for whom the Jew is the enemy."
In another newspaper, Le Figaro, a former antiterrorism judge, Jean-Louis Bruguière, wrote: "In this case, the first elements collected seem to show that there is a phenomenon of self-radicalization that expanded in a rather worrisome way. Many of them haven't traveled to training camps in Afghanistan." He added that he was struck by the fact that "the networks change so fast."
Mr. Prasquier and other Jews across France say that anti-Semitic threats have escalated since the March attacks in and near Toulouse by Mohammed Merah, 23. Mr. Merah had traveled to Pakistan for training and said before he died in a shootout with the police that he was acting on behalf of Al Qaeda.
"Contrary to what we believed or said, the violence of Mr. Merah's act caused emulation among some people," Alain Jakubowicz, the president of the International League Against Racism and Anti-Semitism, was quoted as saying in Libération. "For some young people, this murderer created empathy."
The 11 suspects arrested on Saturday were described in various news reports as admirers of Mr. Merah, and some of them even called his actions "the battle of Toulouse."
Just hours after Mr. Louis-Sidney was killed, blank shots were fired at a synagogue in Argenteuil, a working-class suburb of Paris. "It is an additional act against the Jewish community," said Moshe Cohen-Sabban, a local Jewish leader. "It worries us a lot."
This article originally appeared in The New York Times.