The blockade means Gazans have little to celebrate this Muslim feast-time
The UN special rapporteur on human rights in the Palestinian territories has said Israel's policies there amount to a crime against humanity.
Richard Falk's statement came as UN human rights delegates urged Israel to take nearly 100 measures including ending its blockade of the Gaza Strip.
He said the UN must act to protect the Palestinian population suffering what he called "collective punishment".
Israel says the blockade is a necessary security measure to stem rocket salvos.
The UN Human Rights Council has spent two days reviewing Israel's human rights record under a new mechanism called the Universal Periodic Review (UPR), in which the Council scrutinises the records of all UN member states every four years.
Israel is to report back in March on how it plans to follow-up on 99 recommendations made by the Council, which also include freeing thousands of Palestinian detainees.
Flurry of denunciation
In his statement, Mr Falk called on the United Nations to make an "urgent effort" to "implement the agreed norm of a responsibility to protect a civilian population being collectively punished by policies that amount to a Crime Against Humanity".
He said the International Criminal Court should also investigate whether the Israeli civilian leaders and military commanders for the Gaza siege should be indicted and prosecuted for violations of international criminal law.
The last time there had been "such a flurry of denunciations by normally cautious UN officials" it was during the heyday of the apartheid government in South Africa, Mr Falk said.
"And still Israel maintains its Gaza siege in its full fury, allowing only barely enough food and fuel to enter to stave off mass famine and disease," Mr Falk said.
Israel allowed dozens of trucks filled with humanitarian supplies into Gaza on Tuesday, the fifth such shipment permitted to enter the Hamas-ruled Palestinian territory in the past month.
There were heated exchanges between Israel and some of its adversaries during the debate at the UN last week.
Israeli officials described Gaza as "a hotbed for terrorist preparations" and said more than 200 rockets and mortar shells had been fired from there in the past four weeks. Palestinian militants say their barrages are a response to Israeli violations of a ceasefire in the summer.
Late on Tuesday Israel's ambassador to the UN in Geneva said the country was committed to building on successes in human rights and dealing with any shortcomings, and he welcomed the "positive and productive" dialogue with the Human Rights Council.
However a foreign ministry spokesman dismissed Mr Falk's intervention as "more anti-Israeli propaganda than truth".
"The situation in Gaza is the direct result of the violence inflicted by Hamas, not only on Israeli civilians but the Palestinian population," said Yigal Palmor in an interview with AFP news agency.