Taoiseach Micheál Martin has said the blockading by Israel of food and humanitarian aid to Gaza "clearly constitutes a war crime".
In a keynote address at the Global Ireland Summit in Dublin Castle, the Fianna Fáil leader said the situation must end immediately and criticised what is taking place.
The Taoiseach said the 7 October 2023 attack by Hamas on Israel was "horrific and unjustified".
However, in his starkest words on the conflict to date, he said the "brutal" attacks on Palestine in response are also unjustified, and said the blockading of food and aid is a war crime.
"The horrific and unjustified attack by Hamas on Israel on October 7, 2023, has been followed by the brutal waging of war by Israel in Gaza that has inflicted appalling suffering on Palestinians in Gaza while increasing tensions in an already damaged and fragile region.
"There must be an immediate ceasefire, the release of all remaining hostages and the resumption of unhindered humanitarian assistance to the people of Gaza and at an unprecedented scale," Mr Martin said.
He added: "It has been over 50 days since food, medicines and other essential supplies have not been allowed enter Gaza. Israel's continuing humanitarian blockade is pushing Gaza closer to a hunger crisis. This must be lifted immediately.
"It is simply wrong, in principle and in law, to inflict hunger and suffering on a civilian population, whatever the circumstances. This behaviour clearly constitutes a war crime.
"It is also wholly unacceptable to contemplate the mass displacement of people in Gaza or to talk of permanent occupation. Not only is it an affront to decency and to international law, history tells us it offers no solution" Mr Martin said.
Tánaiste 'sickened' by Israel's blockade of aid in Gaza
Earlier, Tánaiste and Minister for Foreign Affairs Simon Harris said he is "deeply appalled and sickened by Israel's continuing blockade of humanitarian aid in Gaza".
Also speaking at the Global Ireland Summit, Mr Harris called for an end to the violence in the occupied Palestinian territory.
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His comments came as four more children from Gaza were medically evacuated to Ireland.
The children, accompanied by their immediate family members, arrived in Dublin yesterday evening on a plane from Egypt provided by the Norwegian government.
They are the second such group to be brought to Ireland for healthcare treatment after the arrival of eight other children in December.
The group was welcomed by Minister for Health Jennifer Carroll MacNeill, Ambassador of Egypt Mohamed Sarwat Selim and Deputy Head of Mission, Embassy of the State of Palestine Baker MB Hijazi.
Minister Carroll MacNeill said she was pleased Ireland was playing a part in treating children whose lives had been devastated by needless war.
Niall O'Keeffe, Head of International and Migration at the Irish Red Cross said his organisation was supporting Gazan children and their families here to receive medical treatment, as they have been unable to do so at home due to the conflict.
Speaking on RTÉ's News At One, he said: "We are supporting them with accommodation, and then supporting them in their engagement with the medical services and other State agencies which they need to engage with over the next number of weeks."
Mr O'Keefe said there is no fixed date for the next number of children, but some day in the future more families will arrive.
Situation in Gaza 'reaching catastrophic levels'
"The situation in Gaza continues to be and to deteriorate. It is reaching catastrophic levels now in terms of the humanitarian need in the territory.
"The fact that there has been a blockade around the territory for the last nine weeks or so, preventing humanitarian access, it's in complete violation of international humanitarian law, which is the law that we are all supposed to adhere to.
"The situation will only continue to deteriorate for the next while."
He said that children are in Ireland for medical treatment, but they have a much better chance of recovering and dealing with their own situation when their siblings or their mother or parents are with them to support them.
"It's not just the medical attention that they need. They come from a situation which is catastrophic. It's very, very difficult and the trauma that families have experienced over the last number of years, you can only imagine, it's very, very difficult."
Mr O'Keefe said the children are having a good experience with the Irish health system, and being able to get treatment brings great hope to them.
The Department of Justice has co-ordinated visa requirements for the children and their carers and families, while the Department of Social Protection is involved in access to welfare and other supports.
The children will undergo a full medical assessment over the coming week.
It is estimated that Ireland will receive up to 30 paediatric patients in total from Gaza.
The Government approved the initiative to evacuate a number of children from Gaza for treatment in September last year following an appeal from the World Health Organization to address the health needs of those in the territory.
Under the scheme, the children and their families are housed in accommodation managed by the Irish Red Cross and are given a caseworker and translation services.
The Department of Health said the HSE will provide "appropriate psycho-social assessment for both patients and carers".
"All patients and carers received health screening prior to travel," it added.
The Department said doctors from Children's Health Ireland (CHI) worked with the WHO to "identify sick and injured children who would benefit from treatment in Ireland".
The evacuation was conducted with the assistance of the Egyptian government, whose Ministry of Health led coordination efforts and the WHO, which coordinated the evacuation of patients from Gaza to Egypt.
The Irish team worked with Italian colleagues, who provided access to the Umberto Primo Hospital in Cairo for patient assessment.
'Lived through hell'
The Tánaiste said he was "delighted" and "proud" the children were able to travel here for "urgent medical care".
Mr Harris said the children have "lived through hell", adding it is "difficult to imagine the suffering they have experienced".
"While this is positive news, we must keep our focus on the urgent need to stop the conflict," he said.
Mr Harris said Gaza has "received no humanitarian or commercial supplies for many weeks" due to the Israeli blockade.
"The resumption of hostilities has been disastrous, and I urge the parties to return to talks to ensure an immediate ceasefire, allow for unimpeded access of humanitarian aid and the release of all hostages," he said.
Minister Carroll MacNeill thanked the health workers, Irish Red Cross, the Egyptian government, the WHO, the European Union's Civil Protection Mechanism and the government of Norway for their help conducting the operation.
She said Ireland has been "clear" the conflict must stop, adding there is "no justification for the deliberate attacks on civilians and healthcare services in Gaza".
It comes as a senior Hamas official said the group is no longer interested in truce talks with Israel and urged the international community to halt Israel's "hunger war" against Gaza.
Basem Naim was speaking a day after Israel's military said expanded operations in Gaza would include displacing "most" of its residents.
Yesterday, the Hamas-run health ministry in Gaza said at least 2,459 people had been killed since Israel resumed its campaign on 18 March, bringing the overall death toll from the war to 52,567.
Hamas's 7 October attack on Israel resulted in the deaths of 1,218 people on the Israeli side, mostly civilians, according to an AFP tally based on official figures.
Out of the 251 people abducted by militants that day, 58 are still held in Gaza including 34 the Israeli military says are dead.
