Ban Ki-moon says UN shelters must be safe zones and those found guilty of attacking them must be held to account.
The UN secretary-general made his comments after at least 41 Palestinians were killed while sheltering in UN safe zones in Gaza that were shelled in Israeli strikes.
Israel insists it only targeted Hamas fighters during the offensive that killed at least 1,875 Palestinians.
Al Jazeera's Kristen Saloomey reports from the United Nations.
Source: Al Jazeera