At least 15 people have been killed and more than 200 injured when a UN-run school used as a shelter in Gaza was shelled, theGaza health ministry says.
Hundreds of Palestinians were in the school in Beit Hanoun, fleeing heavy fighting in the area.
It is the fourth time that a UN facility has been hit in Israel's offensive against Hamas militants.
In the past 16 days of fighting, more than 750 Palestinians and 33 Israelis have been killed, officials say.
Israel launched its military offensive on 8 July with the declared objective of stopping Hamas firing rockets from Gaza.
Pools of blood Earlier on Thursday, UN humanitarian chief Valerie Amos said that it was "vital" to have a ceasefire.
"We have over 118,000 people now who are sheltering in UN schools... people are running out of food. Water is also a serious concern," she said.