UNITED NATIONS - UN Secretary-General Ban Ki-moon expressed alarm on Wednesday that 20 rockets found hidden in a United Nations school in the Gaza Strip had gone missing and directed the world body to deploy experts to deal with the situation.

The main UN agency in Gaza, UNRWA, found the rockets in one of its vacant schools a week ago. It found a second batch in a vacant school on Tuesday, but said in a statement that because staff were withdrawn quickly, they were "unable to confirm the precise number."

In both cases UNRWA said it "informed the relevant parties," but did not identify who had been contacted. Terrorist group Hamas is the dominant group in the coastal enclave and has been fighting with Israeli troops for the past two weeks.

Ban "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.

cnxps.cmd.push(function () { cnxps({ playerId: '36af7c51-0caf-4741-9824-2c941fc6c17b' }).render('4c4d856e0e6f4e3d808bbc1715e132f6'); });

Ban has asked the UN Department of Safety and Security and the UN Mine Action Service to develop and implement a plan for the safe and secure handling of any weapons discovered on UN premises. Mine Action Service personnel will also be immediately deployed to deal with the situation, the statement said.