Palestinians line up for free food in Rafah. File / AP

The chief of the United Nations' food programme has warned of a "full-blown famine" in northern Gaza and reiterated calls for a ceasefire in Israel's war against Hamas.

"It’s horror," Cindy McCain, executive director of the World Food Programme (WFP) told NBC's "Meet the Press” in an interview to air on Sunday. "There is famine  — full-blown famine  — in the north, and it’s moving its way south."

"What we are asking for and what we've continually asked for is a ceasefire and the ability to have unfettered access to get in safe... into Gaza — various ports, various gate crossings," McCain continued.

She said a ceasefire and a greatly increased flow of aid through land and sea routes was essential to confronting the growing humanitarian catastrophe in Gaza, home to 2.3 million people.

The World Food Programme is one of the many humanitarian groups trying to get aid into Gaza.

The World Health Organisation said on Friday that the availability of food in the Gaza Strip has very slightly improved, though the risk of famine continues in the besieged Palestinian territory.

The aid agencies blame the trickle of essential food into the Palestinian enclave on restrictions and inspections imposed by Israel.

In Gaza, the nutritional treatment for starving children is most urgently needed in the northern part of the Palestinian territory. Civilians have been cut off from most aid supplies, bombarded by Israeli airstrikes and driven into hiding by fighting.

Acute malnutrition rates there among children under 5 have surged from 1% before the war to 30% five months later, the USAID official said. The official called it the fastest such climb in hunger in recent history, more than in grave conflicts and food shortages in Somalia or South Sudan.

Saving the gravely malnourished children in particular requires both greatly increased deliveries of aid and sustained calm in fighting, the official said, so that aid workers can set up treatment facilities around the territory and families can safely bring children in for the sustained treatment needed.

Agencies