The attack hit the entrance of the facility in Rafah, which was housing thousands of Palestinians displaced by the conflict.
Fatah faction leader and resident Ashraf Goma said local people were unable to deal with the casualties. “Bodies of the wounded are bleeding in the streets and other corpses are laid on the road with no one able to recover them,” he said.
UN Secretary-General Ban Ki-moon described the attack as a “moral outrage and a criminal act” and called for those responsible for the “gross violation of international humanitarian law” to be held accountable.
The United States said it was “appalled” by the “disgraceful” shelling by Israel of the school sheltering some 3,000 people in southern Gaza.
In language that was rare in its directness and severity, the US denounced the attack, noting the school had been designated a protected location and that the Israeli army had been informed numerous times of the school’s co-ordinates.
US state department spokeswoman Jen Psaki called on Israel to do “more to meet its own standards and avoid civilian casualties”.
The Israeli military said it was looking into the attack, the second to hit a UN-run school in less than a week.
Amid Hamas accusations that Israel had misled the world about the alleged capture of an Israeli soldier, the officer, Lieutenant Hadar Goldin, was buried yesterday, after the military said it had recovered remains and that he was killed in action.
Lt Goldin’s suspected abduction led to the collapse of a US- and UN-brokered ceasefire on Friday. In Cairo, efforts to find a new truce were due to resume.
Israeli media, on the 27th day of the fighting, reported that most Israeli troops had pulled out of Gaza, and TV footage showed a column of Israeli tanks and dozens of infantrymen leaving the enclave.
An Israeli military spokesman stopped short of calling it a withdrawal, but said residents from some evacuated Gaza neighbourhoods had been told they could return.
“The troops are in the midst of a redeployment to other parts of the border. The mission is ongoing,” Lt-Colonel Peter Lerner said.
The Israeli army claimed more than 55 rockets had been fired from Gaza at Israel yesterday.
Last Wednesday, at least 15 Palestinians who sought refuge in a UN-run school in Jabalya were killed during fighting, and the UN said Israeli artillery had hit the building.
The Israeli military said it was in response to gunmen firing mortar bombs.