Navi Pillay, the United Nations High Commissioner on Human Rights, wants an investigation into what she believes to be war crimes committed by Israeli forces.
She specifically highlighted a recent incident in which Israel attacked a civilian safe house in Gaza, killing more than 30 people.
Her stinging words arrived just one evening before Israel began dropping leaflets on Gaza Saturday, each warning of a coming escalation.
The UN Office for the Coordinator of Humanitarian Affairs reported that 110 Palestinians, all in a single extended family, were "herded" into the house and told not to leave by Israeli soldiers. Less than 24 hours later, the house was attacked.
“Those who survived and were able walked two kilometers to Salah Ed Din road before being transported to the hospital in civilian vehicles," reads the UN report. "Three children, the youngest of whom was five months old, died upon arrival at the hospital.”
Pillay said the attack bore "all the elements of war crimes," according to a published report.
According to the International Committee of the Red Cross, four infants, clinging to the corpses of what was believed to be their parents, were discovered after the attack. The children went undiscovered for over 48 hours, despite Israeli solders being mere yards away.
Pillay, from S. Africa, is a former judge with the International Criminal Court.
Israel denies the incident altogether. The UN report cites specific testimony, though does not identify the origin.
The announcement by the UN commissioner comes on the heels of Red Cross criticism. The aid agency said Israel has failed at helping injured civilians, a key rule of war.
Israel said its military "works in close cooperation with international aid organizations during the fighting so that civilians can be provided with assistance."
"I am concerned with violations of international law," Pillay told Reuters. "Incidents such as this must be investigated because they display elements of what could constitute war crimes."
During the first week of January, the Red Cross criticized Israel for hampering ambulance services to embattled Palestinian civilians.
"The situation is extremely dangerous and the coordination of ambulance services is very complex because of the incessant attacks and military operations," ICRC spokeswoman Dorothea Krimitsas said in Geneva.
"Wounded people have died while waiting for Palestinian Red Crescent ambulances," she added.
Pakistani ambassador Zamir Akram echoed Pillay's sentiment, in a speech delivered on behalf of the Organization of the Islamic Conference.
"In their totality these constitute war crimes and crimes against humanity," he declared.
Daripada Abu Umarah iaitu al-Bara' bin 'Azib radhiallahu anhuma, katanya: "Kita semua diperintah oleh Rasulullah s.a.w. untuk melakukan tujuh perkara, iaitu meninjau orang sakit, mengikuti janazah, menentasymitkan orang yang bersin, menolong orang yang lemah, membantu orang yang teraniaya, meratakan salam dan melaksanakan sumpah."