UN Secretary-General Ban Ki-moon "expresses his outrage and regret at the placing of weapons in a UN-administered school," a United Nations statement said. UNRWA is sheltering 102,000 people in 69 of its schools amid the renewed violence.

"By doing so, those responsible are turning schools into potential military targets, and endangering the lives of innocent children, UN employees working in such facilities and anyone using the UN schools as shelter," the statement said. Ban also expressed alarm over the disappearance of 20 rockets found hidden in one of those schools.