The United Nations, its top leaders and agencies have expressed horror and strong condemnation over the killing of hundreds of civilians in a strike on a hospital in Gaza, underscoring that attack on hospitals or civilian infrastructure is against international humanitarian law and called for holding those responsible to account.

The airstrike on Al-Ahili hospital on Tuesday killed at least 500 people, Gaza's Hamas-run Health Ministry said, blaming Israel for the attack.

Israeli authorities have, however, denied involvement with the Israeli Defence Forces saying rockets misfired by Islamic Jihad militants towards Israel failed after launch and hit the hospital.

“I am horrified by the killing of hundreds of Palestinian civilians in a strike on a hospital in Gaza today, which I strongly condemn. My heart is with the families of the victims. Hospitals and medical personnel are protected under international humanitarian law,” UN Secretary-General Antonio Guterres said on X.

In another post on X, Guterres said too many lives and the fate of the entire region hang in the balance as he called for an “immediate humanitarian ceasefire” in the Middle East to ease epic human suffering.

A statement issued by his spokesperson Stephane Dujarric said Guterres condemned the “strike this evening on Al-Ahli Anglican Episcopal Hospital in Gaza, with preliminary reports of hundreds killed and many others wounded, including women and children”.

He emphasised that hospitals, clinics, medical personnel, and UN premises are explicitly protected under international law, the statement said.

The Secretary-General also condemned the attack on a UNRWA school on Tuesday in Al-Maghazi refugee camp in Gaza which killed at least six people, the statement said.The Secretary-General extended his sincere condolences to the families of the victims and wished a swift recovery to those injured.

President of the 78th session of the United Nations General Assembly Dennis Francis said he is “shocked and horrified” by the attack on Al-Ahli Hospital in Gaza.

“Any attack on hospitals, schools or civilian infrastructure, targeting civilians and taking them hostage, is against international humanitarian law and goes against our common humanity,” Francis said.

“Collective efforts to de-escalate and to facilitate humanitarian access are urgently needed to avoid more bloodshed and civilian casualties.”

UN High Commissioner for Human Rights Volker Turk said in a statement that hospitals are sacrosanct and must be protected at all costs.

“Words fail me. Tonight, hundreds of people were killed – horrifically – in a massive strike at Al-Ahli Arab Hospital in Gaza City, including patients, healthcare workers and families that had been seeking refuge in and around the hospital. Once again the most vulnerable. This is totally unacceptable,” he said.

The top UN Human rights official said that while the full scale of the carnage is yet not known, “what is clear is that the violence and killings must stop at once".

“All states with influence must do everything in their power to bring an end to this horrendous situation. Civilians must be protected, and humanitarian aid must be allowed to reach those in need as a matter of urgency. Those found responsible must be held to account,” Turk said.

The World Health Organisation (WHO) also strongly condemned the attack on the hospital, which was operational with patients, health and caregivers, and internally displaced people sheltering there.

The WHO said the hospital was one of 20 in the north of the Gaza Strip facing evacuation orders from the Israeli military.

“The order for evacuation has been impossible to carry out given the current insecurity, critical condition of many patients, and lack of ambulances, staff, health system bed capacity, and alternative shelter for those displaced,” the global health agency said.

The WHO called for the immediate active protection of civilians and health care. “Evacuation orders must be reversed. International humanitarian law must be abided by, which means health care must be actively protected and never targeted,” it said.

The UN Population Fund (UNFPA) also strongly condemned the strike on the Al-Ahli hospital, saying attacks on civilians and civilian infrastructure must cease and healthcare facilities must never be a target.

In the wake of the attack, the United Arab Emirates and Russia called for an emergency UN Security Council meeting on Palestine, including the strike on the hospital.

Gaza has a population of more than two million and since October 7, when the current conflict began after Hamas launched an audacious terror attack on Israel and the Jewish state declared war on the militant group, about one million Palestinians have been displaced and nearly half of them are sheltering in UNRWA schools in the Gaza Strip.

Dr. Richard Peeperkorn, WHO Representative in the Occupied Palestinian Territory, said people seeking refuge from the conflict "go to these hospitals because they expect they are safe places. Now, even a hospital is not a safe place anymore, what is?”

Before the Al-Alhi Hospital deaths, Israeli strikes on Gaza killed at least 2,778 people and wounded 9,700, according to the Gaza Health Ministry.

Nearly two-thirds of those killed were children, a ministry official said.

Another 1,200 people across Gaza are believed to be buried under the rubble, alive or dead, health authorities said.

Hamas' October 7, attack in southern Israel killed more than 1,400 people, mostly civilians, and resulted in some 200 being taken captive into Gaza. Hamas militants in Gaza have launched rockets every day since, aiming at cities across Israel.