"Hundreds and hundreds of patients" are stuck in hospitals in the north of Gaza, the UN agency for Palestinian refugees said on Monday, reports BBC.
Doctors said Israel told staff to evacuate Al-Quds hospital in Gaza City on Sunday but that moving patients - many of whom are in intensive care - is impossible.
The Palestinian Red Crescent said Israeli air strikes are continuing in the area.
Meanwhile, an Israeli tank and armoured vehicle have cut a key road from the north to south of the Gaza Strip, close to Gaza City.
Israel's military said it is expanding its ground offensive in the territory, saying troops killed "dozens of terrorists" during clashes overnight.
However, the Israeli military has declined to say exactly where their forces are in Gaza - after reports in the last hour that Israeli tanks are on the outskirts of Gaza City and have blocked a key road running north to south.
Israel has been bombing Gaza since the 7 October Hamas attacks that killed 1,400 people and saw 230 people kidnapped as hostages.
On the other hand, the Hamas-run health ministry in Gaza said more than 8,000 people have been killed since Israel's retaliatory bombing began.
Bd-pratidin English/Golam Rosul
