UN High Commissioner for Human Rights Volker Türk said he was “horrified” by reports of mass graves containing hundreds of bodies in two of Gaza’s largest hospitals.

Palestinian civil defense teams began exhuming bodies from a mass grave outside the Nasser Hospital complex in Khan Yunis last week after the withdrawal of Israeli forces. Palestinian officials said 310 bodies had been found in the past week, including 35 in the past day.

“We feel the need to sound the alarm because it is clear that multiple bodies have been discovered,” said Ravina Shamdasani, spokeswoman for the UN High Commissioner for Human Rights.

She described the bodies as “buried deep in the ground and covered with waste,” adding that “among the deceased were the elderly, women, and the wounded,” including some who were bound and stripped of their clothes.

She added: “Some of them had their hands tied, which of course indicates serious violations of international human rights law and international humanitarian law, and must be subject to further investigation.”

Palestinian rescue teams and several UN monitoring missions also reported the discovery of multiple mass grave sites in the Shifa Hospital complex in Gaza City, earlier this month, after Israeli ground forces withdrew after a long siege.

Doctors working for Doctors Without Borders described How Israeli forces attacked Nasser Hospital in late January before withdrawing a month later, leaving the facility unable to function.

Rescue workers continue to dig through the sandy ground to extract bodies outside the hospital. Shamdasani said that her office is working to confirm reports by Palestinian officials that hundreds of bodies were found at the site.

Gaza officials said that the bodies in Al-Nasser Hospital were those of people who died during the siege. The Israeli military on Tuesday rejected allegations of mass burials at the hospital, saying it had exhumed the bodies in an attempt to find hostages taken by Hamas in October.

“The claim that the Israeli army buried Palestinian bodies is unfounded and baseless,” the army said, adding that after examining the bodies, its forces returned them to the place where they had previously been buried.

Israel has repeatedly accused Hamas of operating in hospitals and using medical infrastructure as a shield, something Hamas denies.

The High Commissioner for Human Rights also condemned the increasing number of Israeli air strikes that have struck northern, central and southern Gaza in recent days, including naval artillery fire that has struck buildings along the eastern coast of Gaza.

The air strikes hit many areas that were already reduced to rubble and broken concrete slabs after 200 days of war, including Beit Lahia in the north and downtown Gaza City.

“The north remains in dire straits,” Olga Cherevko, of the United Nations Office for the Coordination of Humanitarian Affairs, said during a visit to the region. “There is more food coming, but there is no money to buy it. Healthcare facilities have been destroyed. There is no fuel to run water wells, and sanitation is a big problem. There is sewage everywhere.”

As Israeli ground forces He reportedly made a short incursion East of Khan Yunis, in the southern Gaza Strip, satellite images from the destroyed city showed a growing camp, which could be intended to shelter people fleeing Rafah in the event of an Israeli ground attack there.

Benjamin Netanyahu, the Israeli Prime Minister, has repeatedly threatened to attack Rafah, the southernmost city of the Gaza Strip, where more than a million people are seeking refuge. On Tuesday, Türk again warned against a large-scale incursion into Rafah, saying it could lead to “more brutal crimes.”

Melanie Ward, head of medical aid for the Palestinians, who recently returned from a visit to Gaza, said an Israeli invasion would be impossible without “human slaughter.”

Ward said that the roads extending north of Rafah towards Deir al-Balah in central Gaza were already crowded with people.

“Every space… is already full of displaced people living in tents,” she said. “People who came from east of Khan Yunis cannot return there because their homes were destroyed. This does not represent enough space for people in Rafah to try to move and seek safety elsewhere. It is impossible for Israel to attack Rafah and not have it be a disaster of epic proportions.”

Many of the recent raids have hit parts of Gaza where displaced people have already fled for the third, fourth or even fifth time.

“There is no safe place to escape to, so we try to do everything we do quickly,” said Rama Abu Amra, a 21-year-old student sleeping with her family in a tent outside a friend’s house in Deir al-Numan. Al-Balah, their fourth location since they fled Gaza City months ago.

She said the tent was uncomfortable, hot during the day and cold at night, and in a crowded area.

When asked where the family could flee to if an evacuation order was issued, she said: “Honestly, we don’t know.”