The exchange comes days before Netanyahu is scheduled to address the United Nations General Assembly in New York.
The latest war of words began after Mamdani, in an interview with CNN on Monday, described Netanyahu as a “war criminal” and an “architect of a horrific genocide of the Palestinian people”.
Responding in a video statement on Tuesday, Netanyahu said he would use his upcoming UN appearance to respond to Mamdani's criticism.
Netanyahu: ‘Shame on you, Mr Mamdani’
“I’m coming to the UN. I’m going to tell the truth about our heroic soldiers, and I’m going to tell the truth about you,” Netanyahu said, referring to Mamdani.
He then directly attacked the New York mayor, saying, “Shame on you, Mr. Mamdani.”
“Shame on you for supporting the Hamas terrorist monsters who butchered our people. Shame on you for inciting riots against New York Jews,” Netanyahu added.
Netanyahu is scheduled to address the UN General Assembly on Thursday, where he has said he intends to defend Israel's military actions and respond to criticism of the country.
Mamdani has backed ICC warrant against Netanyahu
Mamdani has previously said Netanyahu should be arrested if he enters New York, while acknowledging that he does not have the legal authority to carry out such an arrest.
His position is linked to the arrest warrant issued against Netanyahu by the International Criminal Court in 2024 over alleged war crimes and crimes against humanity related to Israel's war in Gaza. Israel rejects the ICC's jurisdiction and denies the allegations.
Mamdani has also repeatedly criticised Israel's military campaign in Gaza. He has rejected accusations of antisemitism, saying his criticism of the Israeli government's policies should not be conflated with hostility towards Jewish people.
Reuters reported that Mamdani has also condemned the October 7, 2023 Hamas attack on Israel.
Netanyahu and Mamdani’s clash escalates
The latest confrontation is not the first time Netanyahu has criticised Mamdani.
The two have clashed over the New York mayor's position on Israel, Gaza and the ICC warrant. Mamdani's earlier comments about potentially arresting Netanyahu during his visit to New York had already drawn criticism from Israeli officials and others.
US President Donald Trump also said in July that Netanyahu would not be arrested while in the United States.
Netanyahu's latest comments come as world leaders gather in New York for the UN General Assembly, with the Gaza war and wider Middle East tensions among the major issues dominating the diplomatic gathering.
Gaza war remains at centre of dispute
The conflict began after Hamas' October 7, 2023 attack on Israel, in which about 1,200 people were killed and 251 people were taken hostage, according to Israeli authorities. Israel subsequently launched a military campaign in Gaza.
More than 73,000 Palestinians have been killed in the conflict, according to Gaza health officials. The figure does not distinguish between combatants and civilians.
Israel rejects accusations that it has committed genocide, saying its military campaign is directed at Hamas.
Meanwhile, the ICC case against Netanyahu remains a major point of contention. The United States and Israel are not members of the court, and Washington has opposed the ICC's actions against Israeli officials.
The Trump administration is also preparing broader sanctions against the court, according to Reuters.
With Netanyahu set to address the UN on Thursday, his latest comments suggest the confrontation with Mamdani is likely to remain part of the political and diplomatic debate surrounding his visit.