An Israeli strike has destroyed the intensive care and surgery departments of the main medical facility in Gaza City, Hamas has said.

Video posted online appeared to show huge flames and smoke rising from Al-Ahli Baptist Hospital after missiles hit a two-storey building. People, including some patients still in hospital beds, were filmed rushing away from the site.

A local journalist said the Israel Defense Forces (IDF) had phoned a doctor and given an evacuation warning.

Hamas called the strike a "horrific crime" by Israel, which said it was looking into the reports.

No casualties have been reported, according to the civil emergency service.

The local journalist, who was working at the hospital, said an Israeli army officer called a doctor operating in the emergency department and asked them to evacuate the hospital immediately.

"All patients and displaced people must go out to a safe distance," the officer reportedly said.

"You have only 20 minutes to leave."

Footage on social media showed staff and patients leaving the building while it was still dark outside.

Dozens of Palestinians, including women and children, were also seen fleeing from a courtyard inside the hospital where they had been seeking shelter.

Al-Ahli - a small medical facility before the war - is now the only hospital still functioning in Gaza City following the destruction of Al-Shifa medical complex and hospitals in the northern part of the Strip.