Israeli forces carried out airstrikes on 20 different locations across the Gaza Strip, reducing a mosque and several homes to rubble and killing five people. (Reuters)

Israeli forces carried out airstrikes on 20 different locations across the Gaza Strip, reducing a mosque and several homes to rubble and killing five people. (Reuters)

An Israeli missile attack that killed 10 civilians sheltering in a U.N. school here early this month prompted a call for restraint from the U.S. government over what the State Department described as a “disgraceful’’ act.

Yet what Israel used in that Aug. 3 strike, according to the United Nations, was a Hellfire missile — a U.S.-made weapon. The incident was one of many in the ongoing six-week-old war in the Gaza Strip in which weapons sold to Israel by the United States and some European nations have played a prominent role.

In the fighting between Israel and the Islamic militant group Hamas, the Palestinian death toll now tops 1,900, with nearly three-fourths of the dead being civilians, according to the United Nations.

Of the arms suppliers that have criticized Israel for those civilian deaths, Spain and Britain have announced plans to suspend or review their exports of arms and military-related equipment to Israel. President Obama has offered similar criticism, but U.S. officials also said in recent days that a new transfer of Hellfires will not be delayed.

Instead, the administration is “just taking extra care to look at these shipments” with “a few additional steps,’’ said State Department spokeswoman Marie Harf.

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Senior Israeli officials have asserted publicly that they use appropriate force. This month, Israeli Prime Minister Benjamin Netanyahu blamed Hamas for the deaths and destruction in Gaza, saying Israel’s military offensive was a necessary response to the group’s continual rocket fire and tunnel networks designed to infiltrate fighters into Israel. “It was justified. It was proportionate,” he said.

But the Palestinian death toll is now far greater than in Israel’s two most recent conflicts with Hamas, in 2009 and 2012. The United Nations has condemned Israel’s use of heavy weaponry in Gaza, and human rights groups have called on the United States to impose a comprehensive arms embargo on the Jewish state.

Some rights activists say that the United States should bear responsibility if a U.N. inquiry now underway finds that Israel’s actions violated international law in part by the use of powerful U.S.-made arms in civilian areas.

“The question that we are asking is: Is that an appropriate munition to be using in a densely populated area?” said Robert Turner, director of operations in Gaza for the United Nations Relief and Works Agency (UNRWA), which helps Palestinian refugees across the Middle East. “According to international law, they need to show precaution, and is their decision of weaponry showing adequate precaution to avoid civilian deaths and casualties?”

Despite the criticisms, current and former analysts and officials say the United States would never halt or reduce weapons supplies to Israel, given the two countries’ close strategic and personal ties.

“It would never happen. It can’t happen,” said Michael Oren, a former Israeli ambassador to the United States. “Israel does not want to change the relationship, and it’s not in the U.S. interest for it to change, either.”

If the Obama administration slowed the Hellfire missile shipment, it would be the first time the United States delayed an arms transfer to Israel in wartime, Israeli officials said. The only previous American-imposed halts came in 1975, when Israel rejected a U.S. proposal for an Egyptian-Israeli peace accord, and in 1981, after an Israeli airstrike on an Iraqi nuclear reactor.

The United States provides roughly $3.1 billion annually in military assistance to Israel, including weapons such as F-16 fighter jets, Apache helicopters, missiles and tank rounds. Washington also largely finances Israel’s Iron Dome missile defense system, which protects Israeli population centers from Hamas rockets fired from Gaza.

The United States and Israel regard Hamas as a terrorist organization. Harf, the State Department spokeswoman, noted that the United States has not stopped providing weapons to Israel during the current conflict and that the Obama administration approved an additional $225 million for the Iron Dome system this month.

Other recent transfers from the United States to Israel have included grenades, mortar rounds and large quantities of rocket motors, human rights officials have said.

“The U.S. government must accept that by repeatedly shipping and paying for such arms on this scale they are exacerbating and further enabling grave abuses to be committed against civilians during the conflict in Gaza,” said Brian Wood, head of arms control and human rights for the advocacy group Amnesty International.

In the debris scattered across much of Gaza, the American origin of many of the weapons fired by Israel has been evident.

In the city of Deir al Balah on a recent day, Gazans found an unexploded bomb lying on the side of the road, steps away from an UNRWA field office. After seeing a photo of the bomb, experts said the weapon was a 2,000-pound U.S.-made Mark 84, one of the largest bombs in the U.S. arsenal.

On a road in Rafah that has been shattered by the tracks of battle tanks and bulldozers, 120mm artillery shell casings lie in the rubble of houses. Some are marked “Made in USA.” A weapon fragment etched with “US” followed by a serial number is labeled: “GUIDED MISSILE, SURFACE ATTACK.” Residents said that tanks had blasted the area and that people were killed and injured.

“What have I ever done to America?” asked Saadi al-Amessi, 48, staring at the fragments of a 155mm artillery shell lying in the remains of his obliterated house in the nearby town of Al Berej.

The United States sells 155mm artillery rounds to Israel, although the country also now produces its own.

Israeli military analysts say that American weaponry and military know-how are the backbone of Israel’s military and are vital to the country’s protection.

“When Israel flies an American-made F-16, it allows Israel to defend itself,” said retired Lt. Col. Reuven Ben Shalom, a former air force pilot who worked as a liaison with the U.S. military.

“If pro-Palestinian groups say the U.S. is helping Israel to do what it does in Gaza, the issue is not whether U.S. weaponry is helping Israel — yes, of course it is,” he said.

Eglash reported from Jerusalem. Anne Gearan and Karen DeYoung in Washington and Griff Witte in Jerusalem contributed to this report.