PARIS—A spate of anti-Semitic incidents has accompanied France’s yellow-vest protests in recent weeks, raising fears that the movement is stirring up hatred in the nation that is home to Europe’s largest Jewish population.
On Saturday, protesters clad in reflective yellow vests were filmed accosting Alain Finkielkraut, a prominent public intellectual, as he walked with his stepmother on the street in Paris, calling him a “dirty Zionist s—” and other insults. A video of the incident went viral online, prompting condemnation from French President Emmanuel Macron and leaders across the French political spectrum.
“The anti-Semitic insults targeting him are the complete negation of who we are and what makes us a great nation,” Mr. Macron said in a tweet. “We will not tolerate them.”
The Paris prosecutor’s office opened an investigation into the incident.
Since the yellow vests, or gilets jaunes, took to the streets in November, a dark undercurrent of violence, conspiracy theories and, at times, outright racism has flourished at the margins of the movement. French police have arrested thousands of rioters and looters; dozens have been charged with assaulting police.
Concerns about anti-Semitism mounted after the previous weekend’s protests. Someone spray painted “Juden” on a Bagelstein, a French chain of bagel restaurants. A Nazi swastika was also spray painted on a portrait of Simone Veil, a French Auschwitz survivor who became president of the European Parliament.
Last week, the government said anti-Semitic incidents in France rose 74% in 2018 compared with the previous year. “Anti-Semitism is spreading like a poison,” said Interior Minister Christophe Castaner.
“You can’t reasonably link that to the gilets jaunes,” Benjamin Griveaux, the French government spokesman, said on Saturday. “But suffice it to say that inside these protests, as a minority, there are elements from the extreme left or extreme right who are anti-Semitic.”
Violence and harassment targeting French Jews have been an acute concern for authorities in recent years, particularly since a series of attacks that began in 2012 with the slaying of four people at a Jewish school in southwestern France. Incidents targeting the Jewish community, at around 500,000 the largest outside the U.S. and Israel, have tended to rise and fall with tensions in the Israeli-Palestinian conflict.
Mr. Finkielkraut, whose father was a Polish Holocaust survivor, is a prominent moderate voice in the French debate over the conflict. He has been sharply critical of Israeli Prime Minister Benjamin Netanyahu, saying in 2017 that Mr. Netanyahu “proposes nothing for the Palestinians. He is pushing them into despair and extremism.”
Mr. Finkielkraut called the Trump administration’s decision to move the U.S. Embassy in Israel to Jerusalem “catastrophic.…It risks setting the region on fire.”
In an interview last week, Mr. Finkielkraut voiced support for the yellow vests but felt the movement had taken a dark turn. “Those left out of the new economy and social welfare have made their voices heard,” he said, but protesters recently “march, destroy without regard for anything or anyone.”
He didn’t respond to a request for comment.
The yellow-vest protests kicked off in November to oppose Mr. Macron’s plans for a fuel-tax increase. They quickly morphed into a broad movement with a menu of demands, including removing Mr. Macron from office, reinstating France’s wealth tax and boosting the purchasing power of the working class. The movement draws many of its supporters from the extremes of French politics and from a growing segment of the French electorate that has become disenchanted with politics altogether.
Polls show that members of the movement tend to get their information from social media, where conspiracy theories can flourish unchecked, rather than mainstream news organizations. A poll published this month found that 44% of people identifying themselves as yellow vests agreed with the idea that there is a global Zionist conspiracy, compared with 22% of French people overall.
In recent weeks, the movement has lost momentum and public support. Just 41,500 protesters took to the streets across the nation on Saturday, one of the lowest turnouts since the protests began. Polls show that while a majority of French still support the yellow vests, a majority also want the weekly protests to stop.
On Saturday, even some leaders on the far ends of the French political spectrum, who have sought to curry favor with the yellow vests, were quick to denounce the treatment of Mr. Finkielkraut.
“The assault on Mr. Finkielkraut is a detestable and shocking act,” far-right leader Marine Le Pen said on Twitter, “illustrating the infiltration of the #giletsjaunes by the anti-Semitic far left.”
Write to Matthew Dalton at Matthew.Dalton@wsj.com