The World Health Organization said it lost communications with its contacts in Al-Shifa Hospital in northern Gaza.
"As horrifying reports of the hospital facing repeated attacks continue to emerge, we assume our contacts joined tens of thousands of displaced people and are fleeing the area," it said.
The WHO added it "has grave concerns for the safety of the health workers, hundreds of sick and injured patients, including babies on life support and displaced people who remain inside the hospital. The number of inpatients is reportedly almost double its capacity."