The World Health Organization said Sunday it had led an assessment mission to Shifa hospital in Gaza City and determined it was a "death zone," urging a full evacuation.

"WHO and partners are urgently developing plans for the immediate evacuation of the remaining patients, staff and their families," the United Nations health agency said in a statement, adding that 291 patients and 25 health workers remained inside the hospital.

WHO said it had headed a joint U.N. team, including public health experts, logistics officers and security staff from a range of agencies on a short and "very high-risk" mission into the hospital on Saturday.