As the Muslim world welcomed the holy month and its customary daytime fast, many Gazans faced bombardment that saw residents once more search through the rubble of destroyed homes for survivors and bodies.
A UN report, citing the health ministry in Hamas-run Gaza, said 25 people have now died from malnutrition and dehydration, most of them children.
The United Nations said "the alarming lack of food, water and health services" is accelerating the crisis "at an unprecedented pace".
Gazans are feeling the shortages even more during Ramadan.
"We don't know what we are going to eat to break the fast," Zaki Abu Mansour, 63, said inside his tent. "I have only a tomato and a cucumber... and I have no money to buy anything."
Goods that are available are sold at exorbitant prices, residents say.
Fighting raged across Gaza, even as UN Secretary-General Antonio Guterres called for "silencing the guns" during the Muslim holy month and said he was "appalled and outraged that conflict is continuing".
Guterres also appealed for removal of "all obstacles" to aid delivery.
