A UN human rights mission began two days of public hearings on Sunday as part of its investigation into alleged violations committed during the devastating war in the Gaza Strip at the turn of the year.
The delegation is headed by Richard Goldstone, a South African judge who previously served as chief prosecutor for international criminal tribunals for the former Yugoslavia and Rwanda.
Investigators plan to publicly interview dozens of victims, witnesses and experts about the 22-day conflict launched by Israel in late December in which more than 1,400 Palestinians and 13 Israelis were killed.
One of the first people to testify was Musa Silawi, a 91-year-old man who recounted an air strike on a mosque in the town of Jabaliya that killed 17 people, including his son and four other members of his extended family.
"After the evening prayers we heard the shell hit the mosque and we had no idea what happened. We all started screaming, 'God help us!'" he said.
"I am 91 years old and I have never seen anything like this catastrophe."
The mission was expected to look into several allegations of human rights violations that emerged in the aftermath of the war.
"The purpose of the public hearings in Gaza and Geneva is to show the faces and broadcast the voices of victims -- all of the victims," Goldstone said last week.
Israeli authorities have so far refused to allow the investigators access to southern Israel and have accused the mission of being pro-Palestinian.
The mission plans to hold similar hearings in Geneva in which they will interview witnesses and experts on alleged violations in Israel and the occupied West Bank, the mission said in a statement.
The UN refugee agency said Israeli fire struck several of its facilities during the war, including schools where civilians were sheltering and a large warehouse filled with humanitarian aid that was set on fire.
Rights groups have also accused Israel of using white phosphorous shells -- which are designed to provide a battlefield smoke screen -- in crowded civilian areas, severely burning several people.
Israel has insisted it made every effort to spare civilians and that all the weapons it used are legal under international law.
It has also said that fighters from the Islamist Hamas movement ruling Gaza operated in crowded residential areas, using civilians as human shields.
On their first visit at the start of June the investigators visited 14 sites in Gaza City and northern Gaza and conducted interviews with several individuals and organisations.
On both visits they had to enter the territory from the Rafah crossing point on the border with Egypt after Israel denied them access through its territory.
The 47-member UN Human Rights Council voted by a large majority in January to set up the probe into accusations of "grave" human rights violations by Israel, but the team was later given a broader mandate to deal with "all violations" during the conflict.
The group plans to produce a final report for the UN Human Rights Council by September 12.