Gaza - Israel said Wednesday the US Senate approval of $13 billion in military aid sent a "strong message" to its enemies as it continued to pummel besieged Gaza.

Fears are rising that Israeli Prime Minister Benjamin Netanyahu will soon follow through on repeated threats to send troops into the southern Gazan city of Rafah, where 1.5 million people are sheltering, many in makeshift encampments.

Israel claims Rafah is the "last" major Hamas stronghold, but aid groups warn any invasion would create an "apocalyptic situation."

Early Wednesday, hospital and security sources in Gaza reported Israeli air strikes in Rafah, as well as the central Nuseirat refugee camp.

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"Everybody seems to be on a countdown to war across the largest displacement camp on Earth, which is Rafah," Norwegian Refugee Council chief Jan Egeland told AFP.

Israel's foreign minister on Wednesday thanked the US Senate for approving the $61-billion military aid package – which includes $13 billion for Israel – hot on the heels of the House of Representatives.

"The Israel aid package that now passed both houses of Congress is a clear testament to the strength of our alliance and sends a strong message to all our enemies," Israel Katz posted on social media site X.

The aid comes against a backdrop of growing protests against Israel's assault on Gaza, which has turned vast areas of the occupied territory to rubble and sparked fears of famine.

Hundreds of students have been arrested in recent days at pro-Palestinian demonstrations on the campuses of leading universities in the United States, Israel's top ally and military supplier.

The United Nations says "multiple obstacles" continue to impede the delivery of urgently needed aid to civilians desperate for food, water, shelter, and medicine.

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The International Court of Justice has ruled there is a "plausible" case Israel is committing genocide in Gaza and has twice ordered provisional measures to ease the suffering of Palestinians.

Nevertheless, Netanyahu has vowed to press on with a planned offensive on Rafah, on the besieged territory's border with Egypt.

Citing Egyptian officials briefed on the Israeli plans, the Wall Street Journal said Israel was planning to move civilians from Rafah to nearby Khan Younis over a period of two to three weeks. Satellite images shared by Maxar Technologies showed tent camps that had recently been set up in that area.

The Journal reported that Israel would then send troops into Rafah gradually in a military operation expected to last six weeks.

In 201 days of siege, Israel has killed at least 34,183 people in Gaza, mostly women and children.

On Tuesday, the United Nations rights office said it was "horrified" at reports of mass graves found at the Gaza Strip's two biggest hospitals after Israeli sieges and raids.

Israel has repeatedly targeted hospitals during the war, accusing Hamas of using them as command centers and to hold hostages abducted on October 7. Hamas denies the accusations.

Gaza's Civil Defense agency said nearly 340 bodies were uncovered of people killed and buried by Israeli forces at the Nasser Hospital in the southern city of Khan Younis.

The Israeli army said claims it had buried Palestinian bodies were "baseless," without directly addressing allegations that Israeli troops were behind the killings.

UN human rights chief Volker Türk called for an "independent" probe into the deaths at the Nasser Hospital and Al-Shifa Hospital in Gaza City, noting the "special protection" awarded to medical facilities under international law.

AFP images from the scene showed numerous bodies under white shrouds in front of the bombed-out Nasser Hospital.

UN human rights office spokesperson Ravina Shamdasani said some of the bodies found at the Nasser Hospital were allegedly "found with their hands tied and stripped of their clothes," adding that efforts were underway to corroborate the reports.

The White House said it would discuss the matter with Israel.

"Obviously scenes of mass graves in general are deeply concerning but I don't have anything that can confirm the veracity of those," National Security Council spokesperson John Kirby told reporters.

The European Union's humanitarian chief Janez Lenarcic called on donor governments to fund the UN Palestinian refugee agency UNRWA, which has been central to aid operations in Gaza.

His comment came after a much-awaited independent report found that "Israel has yet to provide supporting evidence" for its claim that UNRWA employs "terrorists."

After the report was released, UNRWA chief Philippe Lazzarini called for an investigation into the "blatant disregard" for UN operations in Gaza, adding that 180 of the agency's staff have been killed since the siege began.

While some governments have renewed funding for the agency, the United States and the UK are among the holdouts.

The White House would "have to see real progress" before it restores funding, Kirby said.