The Israel Defense Forces has denied accusations from the Hamas-run Gaza Health Ministry that they buried at least 283 bodies in a mass grave near Nasser Hospital in Gaza.

"The claim that the IDF buried Palestinian bodies is baseless and unfounded," the IDF said in a statement. "During the IDF’s operation in the area of Nasser Hospital, in accordance to the effort to locate hostages and missing persons, corpses buried by Palestinians in the area of Nasser Hospital were examined."

"The examination was conducted in a careful manner and exclusively in places where intelligence indicated the possible presence of hostages," the IDF said. "Bodies examined, which did not belong to Israeli hostages, were returned to their place."

White House national security communications adviser John Kirby said Tuesday that the reports of mass graves are "deeply concerning," but the White House is not in a place to validate the reports.

"I wouldn't expect a U.S. investigation," Kirby said, adding, "We'll certainly talk to our Israeli counterparts."

Israel's Ambassador to the United Nations, Gilad Erdan, is claiming that more than 2,135 workers at UNRWA, the U.N. agency for Palestinian refugees, are members of Hamas or the Palestinian Islamic Jihad.

"Hamas has infiltrated UNRWA so deeply that it is no longer possible to determine where UNRWA ends and where Hamas begins," Erdan said. "Israel calls on the donor countries to refrain from transferring their taxpayers' money to UNRWA-Gaza, as these funds will go to the Hamas terrorist organization, and that violates legislation in the donor countries themselves."

This comes after an independent review of UNRWA released on Monday found the agency had policies in place to back up its principle of neutrality, but also found UNRWA had "serious gaps in implementation," The Associated Press reported. The report made recommendations to improve the agency’s neutrality.

The report also found that Israel hadn’t provided evidence to back up its claim that a significant number of UNRWA employees were members of Hamas or PIJ, the AP said.

Iranian Foreign Ministry spokesman Nasser Kanaani called Israel’s retaliatory strike against Iran last week "harassment" that has "caused no damage whatsoever."

"In our opinion, this issue is not worthy of addressing," Kanaani said Monday.

The State Department has released its annual assessment of human rights across the globe.

The U.S. assessed that Israelis have killed or injured nearly 80,000 Palestinians in Gaza -- accounting for 3% of the population.

The State Department stressed that Israel "must conduct military operations in accordance with international law and take every feasible precaution to protect civilians."

"We continue to urgently raise concerns surrounding the deaths of and injuries to tens of thousands of Palestinian civilians in Gaza, including women, children, persons with disabilities, and other vulnerable persons," the U.S. said. "We repeatedly have pressed concerns about Palestinian civilians’ access to humanitarian assistance, displacement of the majority of the population of Gaza, and the unprecedented number of journalists killed."

The U.S. continues to review allegations that Israel violated international laws of war in Gaza and the West Bank, and part of that review will look into whether U.S. weapons were involved, Secretary of State Antony Blinken said at a news conference Monday.

Blinken said the process will be fair, whether a country is "an adversary or competitor, a friend or an ally."

-ABC News’ Chris Boccia