The United Nations human rights chief, Volker Türk, blamed Israel on Tuesday for what he said was the entirely preventable catastrophe of starvation and famine unfolding in Gaza, urging international pressure on the country to allow for the unimpeded entry of humanitarian aid.

International alarm has been growing over the hunger crisis in Gaza, with food experts predicting an imminent famine in the north of the enclave and foreign leaders and diplomats becoming increasingly blunt in pointing the finger at Israel.

“The situation of hunger, starvation and famine is a result of Israel’s extensive restrictions on the entry and distribution of humanitarian aid and commercial goods, displacement of most of the population, as well as the destruction of crucial civilian infrastructure,” Mr. Türk said in a statement.

Mr. Türk said Israel’s restrictions on aid, together with its conduct in its campaign to destroy Hamas, including the displacement of people and the destruction of infrastructure, may amount to the use of starvation as a weapon of war, which is a war crime.

Israel has pushed back on criticism that it is restricting aid from entering Gaza, pointing to its support for several recent initiatives, including efforts to provide supplies by air and sea that aid groups say are far less efficient than road.

It has accused Hamas of diverting aid and of using Palestinian civilians as human shields. The country’s mission in Geneva said on Tuesday that Mr. Türk “seeks once again to blame Israel for the situation and completely absolve the responsibility of the U.N. and Hamas.”

A report released Monday by the U.N.-backed Integrated Food Security Phase Classification said that 1.1 million people, half the population of Gaza, would most likely face catastrophic food insecurity and predicted an imminent rise in hunger-related deaths.

“The coping mechanisms we have seen the past weeks, even months, are people eating bird seeds, animal fodder, wild grass and weeds,” Jens Laerke, a spokesman for the U.N. aid agency in Geneva, told reporters on Tuesday while discussing the report. “We are beyond that. There’s literally nothing left.”

The World Health Organization said on Tuesday that it had set up a center to try to stabilize malnutrition levels in the south of Gaza and was looking to set up another in the north, but it said that to bring in supplies at the scale needed would require a cease-fire. Talks in Qatar are continuing amid another intensive diplomatic push to secure a pause in the fighting.