The attack on the UN school in Rafah where around 3,000 Palestinians who had been made homeless by the violence had been sheltering, injured 30 people, the third such incident within 10 days.
The Egyptian Foreign Ministry, in a statement, strongly condemned the attack.
"Egypt renews its appeal for stop targeting innocent civilians and call for a ceasefire," the statement said.
The UN also expressed "outrage" over the incident with Secretary General Ban Ki-moon describing the attack as "a moral outrage and a criminal act.