Prime Minister Benjamin Netanyahu of Israel took aim at Mayor Zohran Mamdani of New York during his address to the United Nations General Assembly on Thursday, accusing the mayor of antisemitism and saying his criticism of Israel had endangered New York’s Jewish population. Mr. Netanyahu said that since Mr. Mamdani took office, “many Jews no longer feel safe in New York.”

Mr. Mamdani, New York’s first Muslim mayor, has long been an outspoken critic of Israel’s treatment of Palestinians and has denounced Mr. Netanyahu as a war criminal. Mr. Netanyahu has repeatedly assailed the mayor over his views, and many of the claims the prime minister made during his speech echoed his past attacks on Mr. Mamdani. Mr. Mamdani’s stance on Israel has made him a potent political foil for the prime minister, who is in the midst of a critical re-election campaign.

In response to Mr. Netanyahu, Mr. Mamdani accused the prime minister of using his U.N. speech “to repeat baseless lies meant to sanitize his genocide of Palestinians.” “Yet no lie can change the fact that he remains the subject of an International Criminal Court arrest warrant alleging war crimes and crimes against humanity,” the mayor said in a statement. While it was taking place, he was scheduled to join the prime minister of the Netherlands for “a discussion with L.G.B.T.Q.+ youth.”

Shortly before the speech began, Mr. Mamdani posted a wordless, one-minute video on social media that showed him planting an olive tree at Gracie Mansion, his official residence, and eating dinner with Palestinian families from Gaza. “May peace be our future,” the mayor wrote in a caption.