A World Health Organization spokesperson said on Tuesday that three hospitals in Israeli-besieged Gaza had requested help with evacuating patients and that planning had started.

Hospitals have come under bombardment in the Israel-Hamas conflict and all hospitals in the northern part of the enclave have effectively ceased functioning normally, although continue to house some patients that could not flee and displaced Gazans.

WHO spokesperson Christian Lindmeier said evacuations were a last resort. "It's robbing the entire population of the north of the means to seek health (care)," he told a Geneva press briefing. The three hospitals were Al Shifa, from which a group of babies has already been rescued, Indonesian Hospital and Al Ahli Hospital, he said. "So far it's only in planning stages with no further details," he added.

At the same briefing, the U.N. children's agency (UNICEF) warned of the risk of "mass disease outbreak" that could cause child death rates to mount in the densely populated enclave where thousands of people are crammed into overcrowded shelters.

"If children’s access to water and sanitation in Gaza continue to be restricted and insufficient, we will see a tragic – yet entirely avoidable – surge in the number of children dying," said UNICEF spokesperson James Elder.