The World Health Organization says it can no longer contact Al-Shifa Hospital, the largest medical facility in the Gaza Strip.
The WHO said on social media on Sunday that before losing contact, it received a report that "the hospital was surrounded by tanks."
It also said, "There are reports that some of those who fled the hospital have been shot at, wounded, or killed."
The UN health agency expressed grave concern about the safety of health workers, hundreds of patients and people taking shelter at the hospital.
It reiterated its call for an immediate humanitarian ceasefire.
WHO Director-General Tedros Adhanom Ghebreyesus expressed his concerns on social media, describing the situation as "deeply worrisome and frightening."