The head of the United Nations was "horrified" by a strike by Israeli forces on a convoy of ambulances in Gaza on Friday, he said in a statement, adding that the conflict "must stop."
The Palestinian Red Crescent Society has said one of its ambulances was struck "by a missile fired by the Israeli forces" just feet from the entrance to the hospital in Gaza City, in an attack it says killed 15 people and wounded more than 60 others.
"I am horrified by the reported attack in Gaza on an ambulance convoy outside Al Shifa hospital. The images of bodies strewn on the street outside the hospital are harrowing," Antonio Guterres said in the statement.
An AFP journalist at the scene of Friday's attack saw multiple bodies beside the damaged ambulance outside the hospital, which is overcrowded with civilians seeking shelter from Israeli bombing as well as those wounded.
Israel's military said it had launched an air strike on "an ambulance that was identified by forces as being used by a Hamas terrorist cell in close proximity to their position in the battle zone."
Insisting he did "not forget the terror attacks committed in Israel by Hamas," the UN chief added that "for nearly one month, civilians in Gaza, including children and women, have been besieged, denied aid, killed, and bombed out of their homes.
"This must stop," he continued.
The humanitarian situation in Gaza was "horrific," he said.
There is "not nearly enough" food, water and medicine, while fuel to power hospitals and water plants was running out, he warned.
UN shelters in Gaza "are at nearly four times their full capacity and are being hit in bombardments," Guterres continued.
"Morgues are overflowing. Shops are empty. The sanitation situation is abysmal. We are seeing an increase in diseases and respiratory illnesses, especially among children. An entire population is traumatized. Nowhere is safe," he said.
Guterres called again for a ceasefire, and for hostages taken by Hamas in their initial attack on October 7 to be freed.
The Palestinian militant group killed more than 1,400 people in that attack, mainly civilians, Israeli officials say.
Israel has retaliated by bombarding the Gaza Strip, where the Hamas-run health ministry says more than 9,200 people have died, mostly women and children.
Guterres called again for all sides to respect international humanitarian law and protect civilians.
"All those with influence must exert it to ensure respect for the rules of war, end the suffering and avoid a spillover of the conflict that could engulf the whole region," he said.