UN Secretary General Ban Ki-moon strongly condemned the shelling of another UN school in Gaza Sunday, calling it "a moral outrage and a criminal act."
"This madness must stop," Ban said through his spokesman after at least 10 people were killed when a shell hit outside a UN school in Rafah crowded with Palestinian refugees.
It was the third time in 10 days that a UN school has been hit in Gaza, including the Israeli shelling four days ago of a school in Jabaliyah that killed 16 people.
Ban said the latest attack was "yet another gross violation of international humanitarian law," and said the Israel Defence Forces had been repeatedly informed of the UN sites where thousands of Palestinians have taken refuge.
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"This attack, along with other breaches of international law, must be swiftly investigated and those responsible held accountable. It is a moral outrage and a criminal act," he said.
Ban repeated his demand for an immediate ceasefire, saying he was "profoundly dismayed over the appalling escalation of violence and loss of hundreds of Palestinian civilian life since the breach of the humanitarian ceasefire on 1 August."
"The resurgence in fighting has only exacerbated the man-made humanitarian and health crisis wreaking havoc in Gaza," he said.
The 27-day-old conflict has claimed the lives of 1,766 Palestinians, most of them civilians, according to an emergency services spokesman in Gaza.
Since the fighting began, 66 Israelis have been killed, 64 of them soldiers.