In its strongest criticism yet of Israel's military operations in Gaza, the United States has said the shelling of a UN shelter is "totally indefensible".
"The shelling of a UN facility that is housing innocent civilians who are fleeing violence is totally unacceptable and totally indefensible," White House spokesman Josh Earnest said.
At least 15 people were killed on Wednesday, when shellfire hit a UN-run school designated as a civilian shelter in the Jabaliya district of Gaza City.
Israel's Prime Minister Benjamin Netanyahu has said that with or without a ceasefire, Israel is determined to destroy tunnels built by Palestinian militants to infiltrate into Israel from Gaza.
The Israeli military estimated on Wednesday that accomplishing that task, already into its fourth week, would take several more days.
The Pentagon called on Israel to do more to protect civilian life during its military operations in Gaza.
“The civilian casualties in Gaza have been too high. And it's become clear that the Israelis need to do more to live up to their very high standards - their very high and very public standards - for protecting civilian life,” spokesman Colonel Steve Warren said.