UN human rights chief Volker Turk warned on Wednesday there was a heightened risk of “atrocity crimes” in Gaza, urging parties involved to refrain from committing such violations.

According to the UN, the term “atrocity crimes” refers to the crimes of genocide, crimes against humanity and war crimes as defined by international treaties.

“My humanitarian colleagues have described the situation as apocalyptic. In these circumstances, there is a heightened risk of atrocity crimes,” Turk told reporters in Geneva.

“Measures need to be taken urgently, both by the parties concerned and by all states, particularly those with influence, to prevent any such crimes,” he said.

Israeli troops and Hamas militants were locked in fierce ground combat in Gaza on Wednesday after the Israelis reached Khan Younis.

Bombardment in recent days has forced the population to flee to the south of the densely populated Palestinian enclave, where overcrowding and the absence of sanitation could spread disease.

“Some 1.9 million out of the 2.2 million Palestinians have been displaced and are being pushed into ever diminishing and extremely overcrowded places in southern Gaza in unsanitary and unhealthy conditions,” Turk said.

“Humanitarian aid is again virtually cut off as fears of widespread disease and hunger spread.”

Turk said that the only way to end the conflict was to end the Israeli occupation and opt for a two-state solution.

“I think one thing is very clear: it cannot go back to what it was,” he said. Turk’s office requested access to Israel to collect information on the Oct. 7 attacks, including acts of sexual violence but had not received a response from Israel.