The Israeli-besieged Gaza Strip is facing an explosion in child deaths over an alarming lack of food, surging malnutrition and the rampant spread of disease, multiple UN agencies warned Monday.

Nearly 20 weeks into Israel's war on the Palestinian territory, U.N. agencies warned that food and safe water had become "incredibly scarce," adding that virtually all young children had infectious illnesses.

"The Gaza Strip is poised to witness an explosion in preventable child deaths which would compound the already unbearable level of child deaths in Gaza," said Ted Chaiban, deputy head of humanitarian action at the U.N. children's agency UNICEF.

At least 90% of children under 5 in Gaza are affected by one or more infectious diseases, according to a joint assessment by the U.N. agencies for children, food and health.

Nearly 70% had had diarrhea in the two weeks prior to the assessment, marking a 23-fold increase compared to the 2022 baseline.

"Hunger and disease are a deadly combination," World Health Organization emergencies director Mike Ryan said in a statement.

"Hungry, weakened and deeply traumatized children are more likely to get sick, and children who are sick, especially with diarrhea, cannot absorb nutrients well," he said.

"It's dangerous, and tragic, and happening before our eyes."

The Oct. 7 Hamas incursion of southern Israel resulted in the deaths of about 1,160 people, according to an AFP tally of Israeli official figures.

Israel's subsequent assault on Gaza has killed more than 29,000 people, mostly women and children, according to the Gazan Health Ministry.

Since the start of the war, Gaza has been plunged into a nutrition crisis, with outside aid severely restricted.

The U.N. assessment indicated that more than 15% of children under the age of 2 in northern Gaza – one in six – were acutely malnourished, while 3% were suffering from life-threatening severe wasting.

"As the data were collected in January, the situation is likely to be even graver today," the U.N. agencies warned.

In southern Gaza, 5% of children under 2 were acutely malnourished, according to the assessment.

Before the war, only 0.8% of children under 5 in Gaza were considered acutely malnourished, the U.N. agencies pointed out.

"Such a decline in a population's nutritional status in three months is unprecedented globally," they said.