Taoiseach Micheál Martin has told the UN General Assembly that Ireland will act to prevent members of the Israeli government who are "engaged in the unfolding disaster in Gaza" from entering Ireland.
Mr Martin told delegates that Gaza was an example of one of the world's most modern and best equipped armies brought to bear on a trapped and defenceless population.
He said it had been called out for what it is last week by the UN Commission of Inquiry, adding that genocide was the gravest of crimes in international law.
"We cannot say we were not aware," he warned, adding that the International Court of Justice made it clear that states were obliged to use all means to prevent it.
"We will act to prevent those members of the Government of Israel who have been instrumental in fomenting the unfolding disaster in Gaza from entering our country," he said.
Calling on UN states that have influence, he urged them to use it urgently to maximum effect.
Those providing Israel with the means necessary to prosecute its war also needed to reflect carefully on the implications and the effects on the Palestinian people, the Taoiseach said.
Mr Martin's speech came after Israeli Prime Minister Benjamin Netanyahu denounced countries who had embraced Palestinian statehood.
Scores of delegates also walked out of the hall ahead of Mr Netanyahu’s speech.
A Department of Foreign Affairs spokesperson said Ireland was "not present in the General Assembly" for Mr Netanyahu’s speech.
The Taoiseach told those in attendance that Ireland had intervened in the South African case at the ICJ, recognised the State of Palestine and was legislating against the import of goods from the Occupied Territories.
He called for an immediate ceasefire and for those involved to be held accountable.
He said what Hamas carried out on 7 October 2023 was also a monstrous war crime, adding that Hamas, not the Palestinian people, were responsible and Hamas must answer for its crimes.
He said Hamas could have no role in the future governance of Palestine but no crime, however heinous, could justify genocide.
Ireland, the Taoiseach said, stands in solidarity with the Palestinian people.
UN agencies and workers have been at the heart of efforts to preserve and sustain life and prevent the destruction of a people, Mr Martin said, and UNRWA, the agency for Palestinian refugees, had been at the heart of this.
He also paid tribute to medics and journalists risking their own lives.
"What is happening in Gaza cannot be justified or defended. It is an affront to human dignity and decency," Mr Martin said.
He described it as an abandonment of all norms, international rules and law.
Hunger was being used as an instrument of war, he added.
"Babies starving to death while aid rots at the border. People shot whilst desperately seeking food for their families."
Mr Martin said that schools, hospitals, mosques and cultural institutions had also been targeted.
Watch: Taoiseach tells UN world risks return to order of 'might is right'
Mr Martin has told the United Nations General Assembly that the world risks slipping back into an order in which "might is right".
He said that Russia, a founder of the UN and a full-time member of the Security Council, had acted in defiance of the organisation's charter in its illegal, full-scale invasion of Ukraine, prosecuting the war with a willful and reckless indifference to its human consequences.
The country's President, Vladimir Putin, was thumbing his nose at all attempts at a negotiated ceasefire, Mr Martin said, and there were no signs whatsoever that he was ready for peace.
Those in the coalition of the willing - 31 countries that have pledged strengthened support for Ukraine against Russian aggression - would stand with Kyiv for as long as it takes, he told the assembly.
The Taoiseach said that he was deeply concerned by the constant push back on human rights norms that has accelerated in recent years, including the Taliban, for its denial of the most fundamental human rights for women and girls in Afghanistan.
He said that Ireland would compete for a seat on the Human Rights Council from 2027 to 2029.
Conflict was a sign of human failure that could take generations to heal, Mr Martin said, and pointed out that the Irish and British governments had agreed a new framework for addressing the legacy of the Troubles in Northern Ireland.
Remembering members of the Irish Defence Forces who had paid the ultimate price, Mr Martin said that continued support for the United Nations Interim Force in Lebanon (UNIFIL) was essential over the next 15 months to support the efforts of the Lebanese authorities given the complexity and scale of the conflict in the region.
The Taoiseach said the world had also failed Sudan, to our collective shame.
He warned that the human catastrophe in the African country risked wider instability in the region and must be stopped, including the perpetrator of war crimes.
If UN falters, 'leaders have let it down'
The Taoiseach said the UN continues to represent the best of humanity and, if it falters, "it's because we as leaders have let it down".
He said that, 80 years ago, the world was emerging from the most savage conflict in its history with 80 million people lying dead after a deliberate, industrial-scale genocide saw six million people murdered, which he called a monstrous crime that remains unsurpassed in human history.
People were targeted for death because of their ethnic identity, sexual orientation or disability, Mr Martin told the assembly.
He said that when humanity had descended into an abyss, the UN was the phoenix that rose from that darkness as the best attempt to maintain peace and national security, offering a different path for humanity.
Mr Martin called on world leaders to assert and re-insist on the primacy of international cooperation.
Since Ireland joined the UN in 1955 it had been the cornerstone of the country's foreign policy, he added, and there was no other country more committed to its values.
