Just a few weeks ago, Israel, under extraordinary international pressure to respond to warnings of imminent famine in the Gaza Strip, announced new steps to increase humanitarian aid.

But after an Israeli military incursion into the southern city of Rafah this week, the flow of aid has come to a near-total stop, first closed off by Israel and then further restricted, officials say, by Egypt.

Aid officials warned that essentials like food and medicine were running dangerously low, threatening to worsen an already dire humanitarian crisis.

“I’ve never been involved in a situation as devastating, complex or erratic as this,” Hamish Young, the senior emergency coordinator in Gaza for UNICEF, the children’s agency, said on Friday.

Although Israel said it allowed 200,000 liters of fuel into southern Gaza on Friday, that may offer only a temporary respite for hospitals and bakeries, which rely on generators for electricity, U.N. officials said.