UN aid chief Tom Fletcher said the famine was entirely preventable, saying food could not get through to the Palestinian territory "because of systematic obstruction by Israel".

But Israel's foreign ministry immediately hit back, saying "there is no famine in Gaza".

In a statement, it slammed the report by the Rome-based IPC panel, saying it was "based on Hamas lies laundered through organizations with vested interests".

UN agencies have for months been warning of the deteriorating humanitarian situation in the Palestinian territory.

In its latest updated on Friday, the IPC said "as of 15 August 2025, famine (IPC Phase 5) -- with reasonable evidence -- is confirmed in Gaza Governorate", Gaza City, which covers about 20 percent of the Gaza Strip.

Famine is projected to expand to Deir el-Balah and Khan Yunis governorates by the end of September, which would cover around two-thirds of the Palestinian territory.

"After 22 months of relentless conflict, over half a million people in the Gaza Strip are facing catastrophic conditions characterized by starvation, destitution and death," the report said.

This number, based on information gathered between July 1 and August 15, is expected to increase to nearly 641,000 people -- nearly a third of the population -- by the end of September.

The IPC said this was the most severe deterioration in the situation since it began analyzing hunger in the Gaza Strip.

It said the change was driven by a sharp escalation in the war between Israel and Hamas, and the resulting massive displacement of people, combined with the severe restriction of access to humanitarian and commercial supplies of food.

In early March, Israel completely banned aid supplies from Gaza, before allowing very limited quantities to enter at the end of May, leading to severe shortages of food, medicine, and fuel.

Speaking in Geneva, the UN's Fletcher said the famine should "haunt us all".

"It is a famine that we could have prevented if we had been allowed. Yet food stacks up at borders because of systematic obstruction by Israel," he told reporters.

The IPC noted the local food system has also collapsed, with an estimated 98 percent of cropland in the Gaza Strip either damaged, inaccessible or both, livestock decimated and fishing banned.

To add to this, the health system has severely deteriorated, while access to safe drinking water and adequate hygiene has been drastically reduced.

The Integrated Food Security Phase Classification Initiative (IPC) is a coalition of monitors tasked by the UN to warn of impending crises. 

Its definition of a famine has three elements.

Firstly, at least 20 percent of households -- one in five -- must have an extreme lack of food.

Second, at least 30 percent -- one in three -- children under five are acutely malnourished.

And third, at least two in every 10,000 people are dying every day because of outright starvation or because of malnutrition and disease.

Hamas's October 2023 attack on Israel that sparked the war resulted in the deaths of 1,219 people, mostly civilians, according to an AFP tally based on official figures.

Israel's offensive has killed at least 62,192 Palestinians, most of them civilians, according to figures from the health ministry in Hamas-run Gaza that the United Nations considers reliable.