The United States has issued an uncharacteristically severe rebuke to Israel for the shelling of a UN-run school which killed 10 civilians.
A spokesperson for the Department of State called the attack "disgraceful" and said the US was "appalled".
The school, in Rafah in the south of the Gaza strip, was hit on Sunday morning and was a designated protection location which the Israel Defence Forces were aware of and had the coordinates to.
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UN secretary general, Ban Ki-moon, has already described the shelling as "a moral outrage and a criminal act".
It is not the first UN-run school to be hit by Israeli shelling - on Wednesday 15 Palestinians were killed in a similar attack.
That attack was described by the US as "totally unacceptable and totally indefensible" but the language in Sunday's statement is particularly forceful.
The US is a strong backer of Israel providing around $3 billion dollars a year in mainly military aid, the largest amount given to any country.
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Israel's offensive in Gaza has now claimed the lives of around 1,775 Palestinians, mostly civilians and many of them children.
Sixty-four Israeli soldiers have been killed along with three Israeli civilians.
The Palestinian ambassador to the U.N., said on NBC's 'Meet the Press': "What we need now is to stop this fighting, to address the tragic humanitarian situation in the Gaza Strip.
He added putting the people of Gaza "in a continuous situation of confrontation and fighting" will only lead to more violence: "This is an excellent atmosphere for radicalism."
"But if you give them (Palestinians) hope, you open the borders, you let them go to school, let them look for good jobs, let them look for moderation. And we will succeed in allowing all those who want to have peace...to have the upper hand."
The statement from U.S. Department of State spokesperson, Jen Psaki, in full...
"The United States is appalled by today’s disgraceful shelling outside an UNRWA school in Rafah sheltering some 3,000 displaced persons, in which at least ten more Palestinian civilians were tragically killed. The coordinates of the school, like all UN facilities in Gaza, have been repeatedly communicated to the Israeli Defense Forces.
"We once again stress that Israel must do more to meet its own standards and avoid civilian casualties. UN facilities, especially those sheltering civilians, must be protected, and must not be used as bases from which to launch attacks.
"The suspicion that militants are operating nearby does not justify strikes that put at risk the lives of so many innocent civilians. We call for a full and prompt investigation of this incident as well as the recent shelling of other UNRWA schools.
"We continue to underscore that all parties must take all feasible precautions to prevent civilian casualties and protect the civilian population and comply with international humanitarian law."