The United Nations Children's Fund (UNICEF) said on Sunday that more than 13,000 children had died in Gaza as a result of the Israeli attack, adding that many of them suffered from severe malnutrition and did not have "even the energy to cry."

“Thousands of others have been injured or we cannot even locate them,” the organization’s executive director, Katherine Russell, told CBS on Sunday. “They may be trapped under the rubble... We have not seen this rate of deaths among children in almost any other conflict in the world.”

“I have been in the wards for children suffering from severe anemia and malnutrition, and the entire ward is completely quiet,” It added. Because babies and children...don't even have the energy to cry.”

Russell said there were “very significant bureaucratic challenges” to getting aid trucks into Gaza.