The UN rights chief said the "darkest moment" of the conflict in Gaza was unfolding in the north of the territory, warning Friday that Israel's actions could amount to "atrocity crimes".
Volker Turk pointed out that already "more than 150,000 people are reportedly dead, wounded or missing in Gaza" since the war there erupted just over a year ago.
"Unimaginably, the situation is getting worse by the day," he said.
"My gravest fear is, given the intensity, breadth, scale and blatant nature of the Israeli operation currently underway in North Gaza, that number will rise dramatically."
Israel, which has been fighting Hamas in Gaza since last year's deadly October 7 attack, launched a major air and ground assault in the north of the territory this month, saying it wanted to stop the militants from regrouping there.
Turk, the United Nations High Commissioner for Human Rights, warned that Israel's policies in northern Gaza "risk emptying the area of all Palestinians".
"We are facing what could amount to atrocity crimes, including potentially extending to crimes against humanity."
Turk's statement pointed out that Palestinian armed groups also reportedly continue to operate among civilians, including in places of shelter, putting civilians in harm's way "which is totally unacceptable".
- 'Stop the carnage' -
Turk called on the world's leaders to act, stressing that all states are responsible under the Geneva Conventions to ensure respect for international humanitarian law.
"For months, I have pleaded with all parties to the conflict, as well as all states ... to act to stop the carnage and destruction, to ensure the prompt and unconditional release of all hostages, and to ensure international humanitarian and international human rights law are respected," he said.
"But still this goes on and on and on."
His statement stressed the urgency of the situation, warning that "today the darkest moment of the Gaza conflict is unfolding in the north of the Strip, where the Israeli military is effectively subjecting an entire population to bombing, siege and risk of starvation".
"The bombing in North Gaza is non-stop," he said.
At the same time, "the Israeli military has ordered hundreds of thousands to move... But there is no safe way to leave," he warned.
The UN rights chief cautioned that there was "extremely limited access to this part of Gaza, (and) next to no aid has reached the area in weeks".
"Many are now facing starvation."
At the same time, he said, "the Israeli military is striking hospitals, and staff and patients have been killed and injured or forced to evacuate simultaneously".
- 'Genocide Convention' -
The International Court of Justice had made clear Israel's obligation to ensure the entry and delivery of desperately-needed humanitarian aid, Turk pointed out.
In particular, he highlighted the court's binding orders to ensure that Israel conforms with its obligations under the Genocide Convention, obligating other countries to act.
"Under the Genocide Convention, state parties also have the responsibility to act to prevent such a crime, when risk becomes apparent," he said.
Turk warned that "international rule of law is being progressively dismantled", and urged world leaders "not to abandon that minimum of humanity".
"Either the world ashamedly fails those who so desperately need help, or we stand united and put a stop to this."