An Israeli air strike killed 10 people and wounded about 30 on Sunday in a UN-run school in the southern Gaza Strip, a Palestinian official said, as dozens died in Israeli shelling of the enclave and Hamas fired rockets at Israel.
UN Secretary-General Ban Ki-moon described the attack as a "moral outrage and a criminal act" and called for those responsible for the "gross violation of international humanitarian law" to be held accountable.
The United States was "appalled by today's disgraceful shelling" and urged Israel to do more to prevent civilian casualties, according to a statement by State Department spokeswoman Jen Psaki. She also called for an investigation into recent attacks on U.N. schools.
It was the second strike on a school in less than a week.
The Israeli military said it had "targeted three Islamic Jihad terrorists on board a motorcycle in the vicinity of an UNRWA school in Rafah" and added it was "reviewing the consequences of this strike."
Islamic Jihad did not report any of its militants killed or injured in the incident. A Palestinian health official said all those wounded or killed were from inside the school.
Amid Hamas accusations that Israel had misled the world about the alleged capture of an Israeli soldier, the officer, Lieutenant Hadar Goldin, was buried on Sunday after the military said it recovered remains and he was killed in action.
Goldin's suspected abduction led to the collapse of a US and UN brokered ceasefire on Friday. In Cairo, efforts to find a new truce were due to resume on Sunday.