By Gabrielle Tétrault-Farber and Emma Farge

GENEVA (Reuters) -Israeli forces may have repeatedly violated the laws of war and failed to distinguish between civilians and fighters in the Gaza conflict, the U.N. human rights office said on Wednesday.

Separately, the head of a U.N. inquiry accused the Israeli military of carrying out the "extermination" of Palestinians.

In a report on six Israeli attacks that caused many casualties and destroyed civilian infrastructure, the U.N. human rights office (OHCHR) said Israeli forces "may have systematically violated the principles of distinction, proportionality, and precautions in attack".

"The requirement to select means and methods of warfare that avoid or at the very least minimise to every extent civilian harm appears to have been consistently violated in Israel's bombing campaign," U.N. High Commissioner for Human Rights Volker Turk said.

Israel's permanent mission to the United Nations in Geneva characterised the analysis as "factually, legally, and methodologically flawed".

"Since the OHCHR has, at best, a partial factual picture, any attempt to reach legal conclusions is inherently flawed," the Israeli diplomatic mission said.

In a separate meeting of the U.N. Human Rights Council in Geneva, the head of a U.N. Commission of Inquiry, Navi Pillay, said perpetrators of abuses in the conflict must be brought to account.

She repeated findings from a report published last week that both Hamas militants and Israel have committed war crimes but said that Israel alone was responsible for the most serious abuses under international law known as "crimes against humanity".

She said the scale of Palestinian civilian losses amounted to "extermination".

"We found that the immense numbers of civilian casualties in Gaza and widespread destruction of civilian objects and infrastructure were the inevitable result of an intentional strategy to cause maximum damage," Pillay, a former U.N. High Commissioner for Human Rights, told the Geneva meeting.

Israel, which does not cooperate with the inquiry and alleges an anti-Israel bias, chose the mother of a hostage to speak on its behalf and criticised the report on the grounds that it did not give due attention to hostages taken by Hamas on Oct. 7.

"We can do better for them. The hostages need us," Meirav Gonen, the mother of 23-year-old hostage Romi Gonen, said in a tearful appeal.

HEAVY WEAPONRY

Israel's air and ground offensive has killed more than 37,400 people in the Hamas-ruled Palestinian territory, according to health authorities there.

Israel launched its assault after Hamas fighters stormed across the border into southern Israel on Oct. 7, killing around 1,200 people and taking more than 250 people hostage, according to Israeli tallies.

The U.N. rights office report released on Wednesday details six incidents that took place between Oct. 7 and Dec. 2, in which it was able to assess the kinds of weapons, the means and the methods used in these attacks.

"We felt that it was important to get this report out now, especially because in the case of some of these attacks, some eight months have passed, and we are yet to see credible and transparent investigations," said Ravina Shamdasani, spokesperson for the U.N. human rights office.

She added that in the absence of transparent investigations, there would be "a need for international action in this regard".

Pillay also condemned Israel's military methods in Gaza.

"The deliberate use of heavy weapons with large destructive capacity in densely populated areas constitutes an intentional and direct attack on the civilian population," she said.

(Reporting by Gabrielle Tétrault-Farber and Emma Farge; Editing by Howard Goller and Christina Fincher)