Prime Minister Benjamin Netanyahu told world leaders on Thursday that allegations of Israeli genocide in Gaza were not merely false but amounted to “the biggest lie of the century,” delivering a defiant speech in which he asserted his nation’s right to wage war against Iran — a speech that went unheard by scores of delegates who had trooped out before he began speaking.

Netanyahu, his voice rising in emphasis, said that attacking Iran "was one of the easiest decisions I've ever had to make" and denounced as "moral cowards" the many delegates who walked out of the U.N. General Assembly when he took the podium to speak.

“In defending itself, Israel is also defending many of the countries whose delegates have just departed this hall,” Netanyahu said.

“In fact, I would have you know that many of their leaders even express their gratitude to us privately for having taken out Iran’s nukes.”

As Netanyahu approached the rostrum, a mixture of cheers, boos, and mass walkouts erupted.

Scores of delegates marched out, leaving a majority of the visible seats empty thereafter.

“Order in the hall, please,” General Assembly President Khalilur Rahman reiterated.

"If any other moral cowards are still in the hall and have not yet left, please do so now," Netanyahu said.

His remarks — which at times resembled a stump speech as Israel prepares for elections — came after a week filled with speeches by world leaders accusing Israel of genocide and war crimes in Gaza.

In a message to many of the 193 U.N. member nations, the Palestinian Mission to the U.N. urged them to bring as many staff as possible to the assembly hall and to “collectively walk out of the assembly” once the Israeli prime minister is announced.

“This will send a clear message to Netanyahu and his government that no one is willing to aid, abet, or be complicit in its genocide, war crimes, and illegal occupation, which all peace-loving states and peoples demand must come to an end,” the message said.

Israel dismisses allegations that it perpetrated genocide and war crimes and is unlawfully occupying Palestinian territory.

All Israeli settlements are deemed illegal under international law, yet the Israeli government maintains that they are lawful.

Netanyahu, who tends to use visual aids during his General Assembly speeches, at one point held up a pager while reminding the audience of Sept. 17, 2024, when Israel remotely detonated thousands of pagers that had been distributed to the Iran-backed Hezbollah militant group in Lebanon.

The pager attack wounded more than 3,000 people and killed 12, including two children.

He reminded the assembly of the magnitude of the Oct. 7, 2023, attack, in which Hamas militants killed approximately 1,200 people.

“This is equivalent to 40,000 innocent Americans slaughtered in under 24 hours,” he said, or 16 times the death toll of the 9/11 attacks, which claimed nearly 3,000 lives in New York.

Netanyahu expressed gratitude to U.S. President Donald Trump for taking decisive action against Iran, and he insisted Israel would prevail: “We will continue to win because we have no other choice.”

Palestinian President Mahmoud Abbas also addressed the U.N. General Assembly earlier on Thursday, delivering prerecorded remarks from his office in Ramallah, after the United States denied him and other senior Palestinian officials visas to attend the gathering for the second year in a row.

The 90-year-old leader’s popularity at home and relevance abroad have both waned.

Yet in his remarks, Abbas made clear he had no intention of quietly accepting being sidelined.

"We shall not abandon our homeland. We shall not acquiesce to displacement. And we shall not permit anyone to determine our future on our behalf," Abbas said.

Although world leaders repeatedly invoked the plight of Palestinians in speeches throughout the week, Abbas urged the international community to take more tangible action against Israel.

“How much longer will some countries stay silent about Israel, or keep supplying it with weapons that it uses against our people?

The world has seen the enormous cost in the Gaza Strip and the West Bank,” Abbas said.

“What, then, is the international community waiting for before it acts to protect the Palestinian people?”

In past years, Netanyahu has used his General Assembly speech both to denounce the United Nations as biased and to make Israel's case to world leaders.

His address — scheduled for prime time in Israel — is the cornerstone of an abbreviated trip to the United States unfolding under the shadow of New York City Mayor Zohran Mamdani calling him a "war criminal" and pushing for his arrest.

Mamdani has acknowledged that New York lacks the authority to execute an International Criminal Court warrant, but he urged federal authorities to do so.

Israel has become progressively more isolated over the course of the war in Gaza.

The conflict was triggered on Oct. 7, 2023, when militants under Hamas leadership launched an assault on Israel, killing approximately 1,200 people and abducting 251.

According to the Gaza Health Ministry — an arm of the Hamas-run government whose figures are broadly regarded as credible by the international community — at least 73,922 Palestinians have been killed in Israel's ensuing offensive.

A ceasefire agreed to by Israel and Hamas last October halted the heaviest of the fighting and led to the release of the remaining hostages, yet further steps have since stalled.

Israel maintains control of most of Gaza and continues to carry out airstrikes on Palestinians near military-held zones.

Hamas has not disarmed or relinquished power, and there has been no progress toward reconstruction in the mostly destroyed territory.

Netanyahu has said that no Palestinian state will be established while he is Israel's leader, and he has argued that the Palestinian Authority is not a partner for peace.

Netanyahu dismissed incidents of Israeli settler violence against Palestinians in the West Bank as the actions of a “handful of young juvenile delinquents” throwing stones, chopping down olive trees and lighting fires.

“I cannot tolerate that. I will not countenance vigilantism,” the prime minister said before accusing foreign leaders and the international press of distorting the scale of violence in the West Bank.

Netanyahu’s government is overwhelmingly dominated by settlers and their allies, among them the Cabinet minister who oversees the police.

Arrests of settlers implicated in attacks on Palestinians have been conspicuously few.

Israel seized the West Bank and east Jerusalem during the 1967 war, and the Palestinians aspire to incorporate both into their prospective state.

The Palestinians, along with a substantial segment of the international community, regard the settlements as unlawful and as an impediment to the establishment of a viable, contiguous Palestinian state.

Reporters Jennifer Peltz and Edith M. Lederer likewise contributed to this report.