The UN mission probing alleged war crimes in Gaza is holding a second day of public hearings on the Gaza war Monday after listening to emotional testimony from residents who were trapped in the onslaught.

The public hearings are part of the UN Human Rights Council mission's investigation into alleged war crimes during the 22-day offensive launched in late December that killed about 1,400 Palestinians and 13 Israelis.

On Sunday, the mission heard a wheelchair-bound man describe how an Israeli shell slammed into his home, killing 11 of his relatives and cutting off his legs. Another man described a strike on a mosque that killed 17 people.

The group 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, and to issue a final report by September.

The group 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.

Israeli authorities have so far refused to allow the investigators into the country and have accused the mission of bias against the Jewish state.

"The mandate is so one-sided, no fair, thinking person could see it as objective," government spokesman Mark Regev said on Sunday.

"The UN Human Rights Council has over the last months and years totally discredited itself as a serious vehicle for advancing human rights."

The 47-member council voted by a large majority in January to probe accusations of "grave" human rights violations by Israel, but the team was later given a broader mandate to deal with "all violations" during the war, including rocket attacks by Hamas on Southern Israel.

Israel has insisted it made every effort to spare civilians, including dropping thousands of fliers warning residents to flee ahead of strikes.

It has also said that Palestinian fighters and rocket launchers operated in crowded residential areas, using civilians as human shields, a charge also lodged by rights groups against the Islamist Hamas movement ruling Gaza.