The United Nations’ human rights office reported on Tuesday the discovery of mass graves outside of two hospitals in Gaza with hundreds of bodies, including some who were found with their hands tied and stripped of their clothes.

“Among the deceased were allegedly older people, women and wounded, while others were found tied with their hands… tied and stripped of their clothes,” said Ravina Shamdasani, a spokesperson for the U.N. High Commissioner for Human Rights, citing local Palestinian authorities.

At Nasser Hospital in the city of Khan Younis in central Gaza, 283 bodies were found and 42 identified, Shamdasani said. The bodies there were “buried deep in the ground and covered with waste,” the U.N. said. The director of Gaza’s rescue services agency in Khan Younis told CNN that as many as 310 bodies had been discovered as of Tuesday.

Outside Al-Shifa Hospital in Gaza City to the north, 30 Palestinians were found dead in two graves. The bodies at Al-Shifa were found in a grave outside the emergency building and another in front of the dialysis building, Shamdasani said. Twelve have been identified.

“The intentional killing of civilians, detainees and others who are hors de combat is a war crime,” U.N. human rights chief Volker Türk in a release describing him as “horrified.”

The Israel Defense Forces said in a statement to media outlets that claims they buried Palestinian bodies were “baseless and unfounded.” 

Both hospitals have seen some of the heaviest fighting of the war. Al-Shifa was alleged by the Israeli military to host a Hamas base and the U.N. reported that by April 5 it was “an empty shell” with “most equipment reduced to ashes.”

“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 Israeli military said. “The examination was carried out respectfully while maintaining the dignity of the deceased. Bodies examined, which did not belong to Israeli hostages, were returned to their place.”

Gaza’s Health Ministry said as of April 22 that more than 34,000 Palestinians have been killed in Gaza since the war began in October 2023, including 14,685 children and 9,670 women. Over 77,000 have been injured, and at least 7,000 are believed to be missing under rubble.

Over the weekend, Israeli strikes in the southern Gaza city of Rafah, where Israel has vowed to launch a ground offensive, killed 22 people. According to Palestinian health authorities, 18 of the dead were children. The first strike killed a man, his wife and their 3-year-old child, according to the nearby Kuwaiti Hospital, which received the bodies. The woman was pregnant and the doctors saved the baby, the hospital said. The second strike killed 17 children and two women from an extended family.

“Every 10 minutes a child is killed or wounded. They are protected under the laws of war, and yet they are ones who are disproportionately paying the ultimate price in this war,” Türk said on Tuesday, adding a large incursion into Rafah “would risk more deaths, injuries and displacement on a large scale – even further atrocity crimes, for which those responsible would be held accountable.”

The war has devastated Gaza’s two largest cities and left a swath of destruction. Around 80% of the territory’s population has fled to other parts of the besieged coastal enclave. The U.N. has reported thousands are starving and famine is imminent. 

“In the coming days, we will increase the political and military pressure on Hamas because this is the only way to bring back our hostages and achieve victory. We will land more and painful blows on Hamas — soon," Prime Minister Benjamin Netanyahu said in a statement earlier this week.

White House National Security Council spokesperson John Kirby said he was just learning of the U.N. report and called it “deeply concerning,” but could not comment on their veracity during a press briefing aboard Air Force One on Tuesday afternoon. He said not to expect a U.S. investigation.

“Nobody wants to see hospitals become conflict zones. Nobody wants to see fighting in hospitals and around hospitals,” Kirby said while arguing Hamas use of hospitals as command centers necesitates Israeli attacks. “We’ll certainly talk to our Israeli counterparts about it. See what they know.”

In Washington, the Senate was considering a foreign aid package that would send around $17 billion in military aid to Israel and includes another $9 billion in humanitarian aid for Gaza. President Joe Biden has said he will approve the package as soon as it’s sent to his desk.

The Associated Press contributed to this report.