A top UN official said on Friday that hard-hit northern Gaza was now in “full-blown famine" after more than six months of war between Israel and Hamas and severe Israeli restrictions on food deliveries to the Palestinian territory.

Cindy McCain, the American director of the UN World Food Programme, became the most prominent international official so far to declare that trapped civilians in the most cut-off part of Gaza had gone over the brink into famine.

“It's horror," McCain 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."

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.

There was no immediate comment from Israel, which controls entrance into Gaza and says it is beginning to allow in more food and other humanitarian aid through land crossings.

The panel that serves as the internationally recognised monitor for food crises said earlier this year that northern Gaza was on the brink of famine and likely to experience it this month. The next update will not come before this summer.

One of the US Agency for International Development's humanitarian officials in Gaza told The Associated Press that on-the-ground preparations for a new US-led sea route were on track to bring in more food — including treatment for hundreds of thousands of starving children — by early or mid-May. That's when the American military expects to finish building a floating pier to receive the shipments.

Ramping up the delivery of aid on the planned US-backed sea route will be gradual as aid groups test the distribution and security arrangements for relief workers, the USAID official said.