United Nations 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.
"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."
Israeli troops and Hamas militants were locked in fierce ground combat in Gaza on Wednesday after the Israelis reached the southern city of 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 also noted what he called "dehumanizing and inciteful statements" made by high-level Israeli officials and figures from Hamas, which he said could potentially be viewed as incitement to committing atrocity crimes.
"History has shown us where this kind of language can lead," he said. "This is not just unacceptable, but a competent court may view such statements in the circumstances in which they are made as incitement to atrocity crimes."