PARIS – The kidnap, torture, and killing of a Parisian Jew has rekindled worries about anti-Semitism in France, where one of Europe’s oldest plagues is seeping into poor French neighborhoods that are home to many Muslim immigrants and their French-born children.

Jewish leaders had been encouraged by a decline in attacks on Jewish cemeteries, synagogues and community centers from a peak in 2004. But on February 13, police found 23-year-old Ilan Halimi naked, handcuffed, and covered with burns near railroad tracks in the Essonne region south of Paris. He died en route to the hospital.

Authorities say a multiethnic gang that kidnapped the cell phone salesman last month and tortured him for three weeks was after money, reckoning that since he was a Jew, he had to be rich – or at least worth a big ransom.

Interior Minister Nicolas Sarkozy said the gang had tried to kidnap six other people since December, including four Jews.

Some Jewish leaders believe the group didn’t have political motives, but that hatred of Jews may have motivated the violence inflicted on Halimi.

“This case is very serious, because it is the first time in 60 years that a person was killed because he was Jewish,” said Roger Cukierman, head of the Representative Council of French Jewish Institutions.

President Jacques Chirac expressed his sympathy to Halimi’s family for the “barbaric act.” Mr. Chirac, his prime minister and other politicians joined about 1,000 people for a memorial service yesterday night at a Paris synagogue.

“Today, I ask all French citizens to all stand up as one man and shout loud and clear, ‘Enough is enough,'” France’s grand rabbi, Joseph Sitruk, said at the service.

Anti-racism groups planned demonstrations across the country Sunday.

As home to Western Europe’s largest populations of Jews and Muslims, France saw a surge in anti-Semitic crime starting in 2000 after tensions flared between Israelis and Palestinians in the Middle East.

Since then, officials have walked a thin line, making forceful denunciations of anti-Semitism while taking care not to offend a Muslim community estimated at 5 million.

But the enmity between Palestinians and Israelis has fanned Islamic militancy in France and even spilled into classrooms. Some Muslim students, for instance, have refused to attend classes on the Holocaust.

Many French Jews, in turn, were angry that the government let the ailing Palestinian leader Yasser Arafat into France for medical care in 2004. Arafat died in a French military hospital.

Investigators say the gang allegedly involved in Halimi’s death was based in a housing project near Paris – an area like those where unrest erupted last fall and spread through neighborhoods that are home to many Muslims.

“The whole gang is guilty,” Halimi’s mother, Ruth, said in an interview yesterday with AP Television News. “He was a young Jew so he had to be killed.”

“Solutions must be found so this never happens again,” she added.

The suspected gangleader, Youssouf Fofana, was arrested Wednesday as a fugitive in the West African nation of Ivory Coast and is being returned to France, the French and Ivorian governments said.

In an editorial, the newspaper Le Monde said the case is “a sort of looking glass onto the true state of our society.”

Jewish leaders speak of a dangerous brew of televised violence from today’s war zones, anti-Israel fervor and traditional anti-Semitism in Europe and around the world.

Anti-Semitism has existed in Europe as long as Jews have lived here. France’s most prominent case was the Dreyfus Affair, in which a Jewish army captain, Alfred Dreyfus, was falsely accused of treason and sentenced to life in prison in 1894. He was exonerated 12 years later.

Despite recent tensions, authorities say there were signs of a sharp drop in anti-Semitic violence, threats, and intimidation last year, from an all-time high of 970 incidents counted in 2004 by the National Consultative Commission on Human Rights. Final figures for 2005 have not yet been released.