GENEVA - United Nations (UN) human rights chief Volker Turk on Tuesday night issued a statement saying that the massive strike at Al Ahli Arab Hospital in Gaza City that killed hundreds of people is totally unacceptable.

"Words fail me. Tonight, hundreds of people were killed - horrifically - in a massive strike at Al Ahli Arab Hospital in Gaza City, including patients, healthcare workers and families that had been seeking refuge in and around the hospital," he said in the statement.

According to Palestinian sources, at least 500 Palestinians were killed. Local eyewitnesses told Xinhua that a rocket hit the hospital, with a huge explosion ripping through its premises.

"We don't yet know the full scale of this carnage, but what is clear is that the violence and killings must stop at once," Turk said, adding that all countries with influence must do everything in their power to bring an end to this situation.

"Civilians must be protected, and humanitarian aid must be allowed to reach those in need as a matter of urgency," he stressed.

According to media reports, at least six people were also killed Tuesday afternoon when a UN school was hit in a refugee camp in Gaza's middle area. The school had been serving as a shelter for some 4,000 people seeking refuge.

The World Health Organization (WHO) on Tuesday night also issued a statement on the attack on Al Ahli Arab Hospital and reported large-scale casualties, strongly condemning the attack.

WHO stressed that the hospital was operational, with patients, healthcare workers, and internally displaced people sheltering there.

WHO said that the hospital was one of 20 in the north of the Gaza Strip facing evacuation orders from the Israeli military. The order for evacuation has been impossible to carry out given the current insecurity, critical condition of many patients, and lack of ambulances, staff, health system bed capacity, and alternative shelter for those displaced.

WHO calls for the immediate active protection of civilians and healthcare workers, stressing that evacuation orders must be reversed, and the international humanitarian law must be abided by, which means healthcare must be actively protected and never targeted.

In a news comment issued Tuesday night, the International Committee of the Red Cross (ICRC) said it was shocked and horrified by reports that Al Ahli Arab Hospital in Gaza was destroyed and hundreds were killed.

"Hospitals should be sanctuaries to preserve human life, not scenes of death and destruction. No patient should be killed in a hospital bed. No doctors should lose their lives while trying to save others. Hospitals must be protected under international humanitarian law," it said.