A deadly Israeli attack on a school in Gaza has renewed calls for the United States to stop providing staunch support for Israel, including weapons transfers that rights advocates say are fuelling atrocities in the Palestinian enclave.

The Gaza civil defence agency said more than 100 Palestinians were killed and dozens more were injured on Saturday when Israel launched an attack on al-Tabin school in Gaza City.

“The US & allies are claiming a ceasefire is near. But all Palestinians see is more death, dislocation, & despair. The genocide continues,” James Zogby, co-founder and president of the Arab American Institute, wrote on social media.

“It past time to end the charade. Israel doesn’t want peace or a ceasefire. Why are we still sending Israel weapons?”

On Saturday morning, CNN journalist Allegra Goodwin said in a post on X that the US news network had confirmed a “US-made GBU-39 small diameter bomb” was used in the deadly Israeli attack on al-Tabin school. Al Jazeera could not immediately verify that report.

The attack comes as US President Joe Biden has faced months of public pressure to cut off the supply of weapons to Israel amid its war on Gaza, which has killed more than 39,700 Palestinians since early October.

Israel receives at least $3.8bn in US military assistance annually, and Biden signed off on $14bn in additional aid to the US ally earlier this year.

Rights groups also have documented Israel’s use of US-made weapons “in serious violations of international humanitarian and human rights law, and in a manner that is inconsistent with US law and policy” during the war.

But a US Department of State spokesperson announced on Friday that Washington would send an additional $3.5bn to Israel to spend on US-made weapons and military equipment.

‘Ripped to pieces’

The assault on the Gaza City school, which had served as a shelter for thousands of displaced people, also comes amid a renewed push by the US, Qatar and Egypt to get Israel and Hamas to agree to a ceasefire agreement.

But experts have said continued Israeli attacks across Gaza risk derailing those efforts, with some accusing Israeli Prime Minister Benjamin Netanyahu of seeking to sabotage any possible deal to end the war.

The Gaza City school attack was described by paramedics and others at the scene as horrific, with “bodies ripped to pieces”.

Al Jazeera’s Hind Khoudary, reporting from Khan Younis in southern Gaza, said Palestinians sheltering inside the school compound were praying when Israeli forces targeted them with at least three air attacks.

“The civil defence team said that they were able to find 100 dead bodies, but they’re saying that there are more bodies still trapped. Most of the bodies are so disfigured, they’re unable to recognise who these Palestinians are,” Khoudary said.

“People who survived this attack are saying that this is one of the worst days they witnessed since the war started in the Gaza Strip.”

Israel has said, without any evidence, that Hamas and Palestinian Islamic Jihad fighters were operating from the school – a claim that was rejected by Hamas.

US National Security Council spokesperson Sean Savett said in a statement on Saturday that “far too many civilians continue to be killed and wounded” and called for a ceasefire and a hostage deal.

Echoing Israel’s claims without providing evidence, he added: “We know Hamas has been using schools as locations to gather and operate out of, but we have also said repeatedly and consistently that Israel must take measures to minimise civilian harm.”

‘No more bomb shipments’

Meanwhile, a spokesperson for Palestinian President Mahmoud Abbas has urged the US to end its “blind support [for Israel] that leads to the killing of thousands of innocent civilians, including children, women, and the elderly”.

Nabil Abu Rudeineh said in a statement that US weapons transfers to Israel made it “directly responsible for this massacre [at al-Tabin school] and for the continuation of the Israeli onslaught on the Gaza Strip for the tenth month running”, as reported by the Wafa news agency.

US rights advocates also renewed their push for the Biden administration to end its arms transfers to Israel following the school attack.

Sarah Leah Whitson, executive director of US-based advocacy group Democracy for the Arab World Now, criticised the arms sales as “Pavlovian conditioning for a feral army”.

The Council on American-Islamic Relations (CAIR), a US-Muslim civil rights organisation, also said the Gaza City attack merits a serious response from the Biden administration.

“If President Biden gives a damn about human life, he will respond to this act of state terrorism by immediately stopping the flow of weapons to the Israeli government and forcing Netanyahu to agree to the ceasefire deal that he keeps sabotaging,” CAIR wrote on X.

“No more calls for Israel to investigate itself. No more bomb shipments. This US-enabled genocide must end now.”

Former Israeli government adviser Daniel Levy also told Al Jazeera on Saturday that the $3.5bn US military finance package for Israel showed the “dishonesty and duplicity of the US administration”.

Levy said Washington showed “humiliating weakness” when it stated that Biden “got really angry” in a recent call with Netanyahu, but then handed the Israeli prime minister another $3.5bn in funding for weapons.

“We have to see that it’s not just weakness. It’s also ideological alignment. The US government is the guarantor of the axis of Zionist extremism,” Levy said. “They may not like some of the details, but this is what they are backing.”