Aid workers report seeing people thin and visibly starving with sunken eyes.
Hunger stalks the entire Gaza Strip, where 2.3 million people live under Israeli bombardment.
The United Nations warned this week that pockets of Gaza face famine.
Areas near the Egyptian border get limited supplies of imported food.
But not the north, says World Health Organization emergency coordinator Sean Casey.
"The food situation in the north is absolutely horrific. There's almost no food available and everybody we talk to begs for food and comes to us and asks: where's the food?"
Medics in Gaza hospitals describe babies born sick to malnourished mothers, infants losing weight, mothers unable to produce breast milk and injured patients too weak from hunger to fight off infection.
Jabr al-Shaer is a pediatrics doctor at Al-Najjar Hospital in Rafah.
"A month and a half ago, this baby's weight was 7.5 kilos. In a month and a half, he lost nearly two kilos, his weight now is 5.5 kilos. The mother and the baby suffer from malnutrition, no milk is available, which all impacts the growth of the baby. He lost two kilos, this is bad. It impacts his immunity. He constantly has inflammation in the chest and gastroenteritis."
Scenes of chaos and gunfire during an aid distribution in Gaza City in this video verified by Reuters.
"Now the occupation forces are opening fire at citizens as they receive humanitarian aid in the north of the (Gaza) Strip, in Al Zeitoun neighborhood. This is the sound of gunfire. These are the scenes."
At the start of the war, after a Hamas assault that killed more than 1,200 people, Israel announced it was cutting off all supplies to Gaza.
It has since let in humanitarian aid but far less is entering the enclave now than before.
Palestinians interviewed by Reuters said they often went days without eating, or could only eat once a day.
What food is commercially available is often unaffordable.
In Khan Younis, Palestinian mother Hanaa Noufal is displaced, like most Gazans. She opens a single can of beans for her five children.
"It has been nearly 100 days while eating this canned food. The children are suffering a lot and getting sick, the situation is really bad for them, they have a lot of diseases, we cannot even bring medications for them. It is difficult to bring medications. What can I tell you? There are no supplies to buy, we are all depending on canned food, and the canned food is really bad."
No comprehensive data on hunger is available for Gaza, with aid agencies struggling to move and communicate amid the fighting.
UNICEF projects that in the coming weeks more than 10,000 children in Gaza risk wasting, one of the most serious results of malnutrition, which can stunt physical growth and brain development.
Heather Stobaugh of Action Against Hunger, says children are at highest risk of dying.
"So the severe acute malnutrition that you've mentioned before is the deadliest form of hunger and it's the biggest threat right now in Gaza."
Aid agencies say Israeli checks are hampering aid deliveries into Gaza and the military prevents distribution outside the southern area around Rafah.
Israeli government spokesperson Eylon Levy has denied such limitations and put any problems down to U.N. distribution capacity.
