Medics care for injured Palestinians following Israeli bombardment at the Kuwaiti Hospital in Rafah. AFP

Tedros Adhanom Ghebreyesus also hailed Gaza's medical workers who continue their work under increasingly dire circumstances.

"The decimation of the Gaza health system is a tragedy," he posted on X, formerly Twitter. "We persist in calling for CeasefireNow."

"In the face of constant insecurity and inflows of wounded patients, we see doctors, nurses, ambulance drivers and more continue striving to save lives," Tedros said.

The UN health agency has long been sounding the alarm about the state of health care since the bloodiest ever war in Gaza erupted following Hamas's unprecedented attack inside Israel on October 7.

Vast areas of Gaza lie in ruins and its 2.4 million people have endured dire shortages of water, food, fuel and medicine due to an Israeli siege, alleviated only by the limited arrival of aid trucks.

‘Unbearable'

Of Gaza's original 36 hospitals, only nine are now partially functional, all of them in the south and all of them overwhelmed. After missions last week to two badly damaged hospitals in the north, Al Shifa and Al Ahli, WHO staff described "unbearable" scenes of largely abandoned patients, including young children, begging for food and water.

WHO warned that even as healthcare needs soar, only 38 per cent of pre-conflict hospital beds remained available in the Palestinian territory and only 30 per cent of original health staff were still working.

At the same time, hospitals, protected under international humanitarian law, have repeatedly been hit by Israeli strikes since the war erupted.

As of Dec.20, WHO had registered 246 attacks on health care in Gaza, including hospitals and ambulances, resulting in 582 deaths and 748 injuries.