Hospitals in Gaza City are under immense pressure, the World Health Organization (WHO) said Tuesday.

Patients in Al-Shifa Medical Complex's emergency department were seen laying on the floor while waiting for treatment in footage released by WHO.

Al-Shifa's emergency physician Dr Ismail Ramadan, said that there were long waiting lists for the seriously injured.

"Unfortunately, we have to make choices between them. Between saving lives. Between children. Between the elderly," Ramadan said on Sunday.

In Gaza City's Al-Rantisi Children's Hospital, medical staff struggle to treat children in the paediatric intensive care unit due to a lack of resources, including critical medicines and MRI machines.

Dr Mohammad Hejoh, the hospital's head of paediatric intensive care unit, said he and his staff were facing "psychological pressure."

"We are unable to stay focused as we have no idea where to focus; should we keep our focus with the patients or our families at home?" Said Hejoh.

Almost half of all functional hospitals are in Gaza City, WHO said.

Israel launched its offensive in Gaza City on Tuesday, vowing to overwhelm a city already in ruins from nearly two years of war as thousands of Palestinians fled in vehicles strapped with mattresses and other belongings that clogged a coastal road.

The operation into the largest Palestinian city escalated a conflict that has roiled the Middle East and likely pushed any ceasefire with Hamas farther out of reach. The military would not offer a timeline for the offensive that aims to crush the militant group's ability to fight, but Israeli media suggested it could take months.

“Gaza is burning,” Israeli Defense Minister Israel Katz declared as the operation began. Heavy bombardment pounded the city, and troops began moving in from the outskirts after weeks of airstrikes and buildup toward the renewed assault.

The offensive began the same day that independent experts commissioned by the United Nations Human Rights Council accused Israel of committing genocide in Gaza. Israel rejected the allegation, calling the report “distorted and false.”

An estimated 1 million Palestinians were living in the Gaza City region before warnings to evacuate began ahead of the offensive, and the Israeli military estimates 350,000 people have left the city.