"The cost of meeting the needs of 2.7 million people - that is the entire population of Gaza and 500,000 people in the occupied West Bank - is estimated to be $1.2 billion," the UN Office for the Coordination of Humanitarian Affairs (OCHA) said.

"The original appeal, launched 12 October, asked for $294 million to support nearly 1.3 million people. The situation has grown increasingly desperate since then," it added.

OCHA said the new appeal will outline the need for food, water, health care, shelter, hygiene and other urgent priorities following the massive bombardments in the Gaza Strip.

"We urge donors to promptly make resources available for the response," it added.

"Our ability to ease the suffering of the Palestinian population will depend on adequate funding; safe and sustained access to all people in need, wherever they are; sufficient flow of humanitarian supplies; and - importantly - fuel."

A group of UN-mandated human rights experts, including the special rapporteur on the occupied Palestinian territories, said Thursday that "time is running out to prevent genocide and humanitarian catastrophe in Gaza".

"We remain convinced that the Palestinian people are at grave risk of genocide," the experts said in a joint statement.

"The time for action is now. Israel's allies also bear responsibility and must act now to prevent its disastrous course of action.", they noted.

Since the war broke out on 7 October, 9,061 Palestinians were killed in Gaza by Israeli airstrikes, with an additional 140 Palestinians killed by Israel in the occupied West Bank.