At least 576,000 people in the Gaza Strip - one quarter of the population - are one step away from famine, a senior UN aid official told the Security Council on Tuesday, warning that widespread famine could be "almost inevitable" without action.

"Very little will be possible while hostilities continue and while there is a risk that they will spread into the overcrowded areas in the south of Gaza. We therefore reiterate our call for a ceasefire," said Ramesh Rajasingham, coordination director of the UN Office for the Coordination of Humanitarian Affairs, Reuters reported.

One in six children under age 2 in northern Gaza suffers from acute malnutrition and wasting and practically all the 2.3 million people in the Palestinian enclave rely on "woefully inadequate" food aid to survive, he told the Security Council.

Rajasingham said the UN and aid groups face "overwhelming obstacles just to get a bare minimum of supplies into Gaza." These include crossing closures, restrictions on movement and communication, onerous vetting procedures, unrest, damaged roads and unexploded ordnance, he said.