On Wednesday, the United Nations denounced Israel for shelling a UN school being used as a civilian shelter in the Gaza Strip. The attack killed 16 people and was the second such UN facility to be hit in recent days. Secretary General Ban Ki-Moon said the attack was "unjustifiable," stating "I condemn this attack in the strongest possible terms." The U.S. also condemned the attack on Wednesday. Seperately, an Israeli airstrike on a crowded shopping area Wednesday killed 15 people and wounded more than 150. Israel said the attack on the school was launched after soliders were receiving mortar rounds from the vicinity of the facility. The U.N. has urged an immediate humanitarian ceasefire.