When a wave of rioting erupted across France last fall, a Jewish youth group swung into action to guard synagogues and community centers from possible anti-Semitic spillover violence. Many Jews feel that such a reflex is needed these days in France, home to the largest population of both Jews and Muslims in western Europe and sporadically simmering with tensions. As Israeli Prime Minister Ehud Olmert was greeted with a red-carpet welcome in Paris on Wednesday, he faced a France where anti-Semitic attacks have tumbled from a high in 2004, despite several dramatic incidents. Olmert called President Jacques Chirac "one of the world's great fighters against anti-Semitism." But others within the Jewish community also are keeping watch. Formed in 2000, the Jewish Defense League - which has no ties to the U.S. Jewish Defense League - groups about 100 to 150 Jewish teens and young men to protect their community, experts say. "Jews are fed up," said a league member named Maxime who refused to give his full name, saying he feared for his safety. "We've been nice for 30 years. Now, we gather and fight back." Maxime, a 22-year-old waiter, admits his group is not afraid to take justice into its own hands if need be. He bragged about a 2003 incident in which a Jewish Defense League member beat up pro-Palestinian university students, injuring one. "If a (Jewish) kid gets beaten up at school a few times, we go there and talk to the guy who beat him up," he said. "If he does it again, we go back and it's another story." "Investigations are useless," Maxime said. "We're a second police." Group members are unarmed but train in Krav-maga, a form of close combat developed by the predecessor of the Israeli Army. Apparently tolerated by authorities, they patrol Jewish neighborhoods such as Paris' Marais and keep watch in community centers and even synagogues to keep any subversives at bay. Members wear scarves or masks but not uniforms and move quickly to protect Jewish sites when they feel it necessary, like during the riots that spread through poor French suburbs last fall. Jean-Yves Camus, a researcher with the European Center of Research and Action on Racism and Anti-Semitism, said the group epitomizes a new generation of young Jews. "LDJ is the symbol of a generation that says: 'We won't bow our heads,"' Camus said in an interview. Analysts say the anti-Semitism threat is evolving. For years, far-right groups were the greatest concern. Now, the epicenter of anti-Semitism is reported to be among immigrants from North Africa and their French-born children. League leaders fault what they say is the powerlessness of mainstream associations in stemming the periodic waves of anti-Semitism. Early this year, a young Jewish man was kidnapped, tortured and left for dead by a gang allegedly led by a man from Ivory Coast. Last month, a group of militant young black men who call themselves the Ka Tribe swarmed into Paris' Jewish quarter shouting anti-Semitic slogans and scrapping for a fight with league members. Celine Ruimy, a 45-year-old housewife in the Jewish quarter, is glad the group exists. "It's important to show that there are some things we can't accept and there are things we are not willing to live through again," she said. Butcher shop owner Linda Saada, 47, agrees. "I told my nephews, who are religious, to wear a cap instead of a kipah," she said. "I think it's more prudent," she said. Roger Cukierman, who heads the umbrella Representative Council of Jewish Organizations in France, refused to comment on the Jewish Defense League.