According to the international organization's report, all the hospitals in the Palestinian coastal enclave, including private clinics, have beds for a total of 2,000 people. In addition, medical facilities lack medicines and equipment.
"Hospitals have to discharge patients who have less serious injuries than others," the Cairo office of the UN Office for Coordination of Humanitarian Affairs (OCHA) was quoted as saying.
The organization also warned that Gaza was on the verge of a humanitarian crisis with flour reserves almost exhausted. It added that blackouts could follow as the enclave's sole power plant would run out of fuel later on Monday.
The regional office of the World Health Organization (WHO) has issued a statement, urging both parties to stop military actions and to open Gaza borders for humanitarian deliveries of food, medicines and fuel.
The WHO said it would send medicines and equipment for approximately 5,000 patients.
Saudi Arabia has sent two hospital aircraft with medical personnel to Gaza to help those injured and to transport severely injured patients to Saudi hospitals.
Health Minister Hamad bin Abdallah al-Manai told the state-run SPA agency that the country's hospitals were prepared to receive injured from Gaza.
According to recent data provided by the Palestinian medics, over 300 people have been killed and over 700 injured since Israel began large-scale airstrikes on Gaza on Saturday in response to rocket and mortar fire by Palestinian militants.
No official death toll has been released, but according to the local human rights organizations, at least 20 children and nine women were killed in the first hours of Israeli airstrikes.
