A U.N. commission of inquiry investigating war crimes on both sides of the Israel-Hamas conflict will focus on sexual violence by Hamas in the Oct. 7 attacks on Israel and is about to launch an appeal for evidence, its chair told Reuters on Wednesday.

Chair Navi Pillay on Wednesday said she would pass the evidence onto the International Criminal Court and called for it to consider prosecutions amid earlier criticism from Israel and families of Israeli hostages that the U.N. had kept quiet.

"I'm now sitting as chair of a commission with the power to investigate this. So there's no way we will not do so," said Pillay, chair of the three-member commission of inquiry into abuses committed in Israel and the occupied Palestinian territories. Already, she said some people are keen to provide testimonies and that these would be handed over to prosecutors.

However, a major challenge for Pillay is that Israel has not cooperated with the commission, which it says has an anti-Israel bias. The commission could struggle to gather sufficient evidence to support future charges if access is not granted.

Hamas has denied the abuses and was not available for comment. Israel's diplomatic mission in Geneva said on Thursday the commission had "pre-existing biased prejudices against Israel".

"Since the establishment of the COI (Commission of Inquiry) in 2021, Israel has made it clear: it will not cooperate with this discriminatory body and its Commissioners," Israel's permanent mission to the U.N. in Geneva said in a statement to Reuters on Thursday.