“WHO and partners are urgently developing plans for the immediate evacuation of the remaining patients, staff and their families,” it said.
“Over the next 24 to 72 hours, pending guarantees of safe passage by parties to the conflict, additional missions are being arranged to urgently transport patients” to other hospitals in the south of Gaza.
The Israeli military did not immediately comment on the WHO statement or the visit.
The remaining 2,500 internally displaced people who had sought refuge on Al Shifa grounds were gone after the Israeli Defense Forces issued evacuation orders on Saturday, WHO said.
Israeli forces seized Al Shifa in their offensive across north Gaza last week, saying it concealed an underground Hamas command centre. The military said it found evidence of a Hamas base underground. Al Shifa staff say Israel has proven no such thing.
The visit was coordinated with the Israeli military to reduce risks but occurred in an active conflict zone, with heavy fighting close to the hospital, WHO said.
WHO repeated its call for an immediate ceasefire and sustained humanitarian assistance, saying options for medical care in the small coastal enclave were dwindling.