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The head of the Anti-Defamation League (ADL) issued a warning to New Yorkers after Zohran Mamdani was elected the next mayor of New York City, calling him a "clear and present danger" to the Jewish community and vowing to hold him accountable.

"Hundreds of thousands of Jewish New Yorkers are alarmed, and that anxiety is well-placed," said ADL CEO Jonathan Greenblatt on Fox News Radio's "Brian Kilmeade Show."

Mamdani was declared the winner of the mayoral race Tuesday night, defeating former Gov. Andrew Cuomo and Curtis Sliwa. The self-described democratic socialist has faced intensifying scrutiny for past remarks labeled antisemitic by opponents.

Zohran Mamdani speaks to supporters during a campaign event in Brooklyn.

Democratic New York City mayoral candidate Zohran Mamdani attends a campaign event in Brooklyn Nov. 1. (Stephanie Keith/Getty Images)

"We have learned as Jews over the years to believe people when they tell you they're going to do something, like take them at their word," Greenblatt said Wednesday.

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"This mayor-elect, if you will, has said things and committed to do things that may very well make this environment even more unsafe for Jewish New Yorkers."

Greenblatt noted he’s seen a rise in antisemitism in the city and that New Yorkers are now on edge with the election of Mamdani.

Zohran Mamdani delivers victory speech on Election night with his banner behind him.

Zohran Mamdani delivers a victory speech at a mayoral election night watch party Tuesday in New York City.  (Yuki Iwamura/AP)

The 34-year-old former state assemblyman from Queens has repeatedly refused to condemn the slogan "globalize the intifada." The phrase had been widely used by anti-Israel protesters and has been interpreted as a call for violence against the Jewish state.

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The mayor-elect was also criticized for posting a photo of him smiling with Imam Siraj Wahhaj, who served as a character witness for the mastermind of the 1993 World Trade Center bombing. Wahhaj also had a history of defending convicted terrorists and raised funds for their legal defense.

In response to Mamdani’s rise, Greenblatt said the ADL has launched several initiatives, including a tip line for New Yorkers to log incidents of antisemitism.

"If New Yorkers experience antisemitism, where they work or where they worship or where they shop or where they socialize, tell us at ADL, and we will make sure that the authorities follow up," he said.

Zohran Mamdani celebrates on stage with Bernie Sanders and Alexandria Ocasio-Cortez during a campaign rally in Queens, New York.

New York City mayoral candidate Zohran Mamdani, center, celebrates with Sen. Bernie Sanders, left, and Rep. Alexandria Ocasio-Cortez, right, during an election rally at Forest Hills Stadium in Queens Oct. 26. (Andres Kudacki/Getty Images)

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Greenblatt said the ADL also launched something he called the "Mamdani Monitor," which will track which officials the next mayor appoints and policies and programs he implements.

"We are going to hold this guy accountable," Greenblatt vowed.

Mamdani has strongly denied accusations of antisemitism, saying his criticism is directed at the Israeli government, not Jewish people. He has previously vowed to arrest Israeli Prime Minister Benjamin Netanyahu if he were to enter New York City.

He reaffirmed that position during an appearance on "The Story" in October.

New York Attorney General Letitia James and mayoral candidate Zohran Mamdani attend a campaign rally.

New York Attorney General Letitia James and mayoral candidate Zohran Mamdani attend a campaign rally at Lou Gehrig Plaza in the Bronx, where Mamdani received endorsements from Bronx elected officials Sept. 2. (Lev Radin/Pacific Press/LightRocket via Getty Images)

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"I've said that this is a city that believes in international law, and this is a city that wants to uplift and uphold those beliefs," Mamdani said.

The International Criminal Court has accused Netanyahu of "war crimes" over Israel’s war with Hamas, which the Hamas-run Gaza Health Ministry says killed more than 67,000 people.