(AFP) - The UN human rights chief on Thursday highlighted allegations of serious rights violations in the Israel-Hamas war that he said needed "full accountability".

Volker Turk said "extremely serious allegations of multiple and profound breaches of international humanitarian law, whoever commits them, demand rigorous investigation and full accountability".

The UN high commissioner for human rights did not name Israel or Hamas, but he spoke after a visit last week to the Middle East, where he warned that both sides were committing war crimes in a conflict that has left thousands dead.

"Where national authorities prove unwilling or unable to carry out such investigations, and where there are contested narratives on particularly significant incidents, international investigation is called for," he said in a briefing to UN member states in Geneva.

Israel has vowed to eradicate Hamas in retaliation for the attacks of October 7, which it says killed 1,200 people, most of them civilians.

Hamas also took 239 people hostage, among them elderly people and young children, according to authorities.

Israel's relentless bombardment and ground offensive in Gaza has killed more than 11,500 people, also mainly civilians and including thousands of children, according to the Hamas-run health ministry.

- Israel refuses access -

Turk decried the "conflagration of violence (that) has been unleashed".

He said he had spoken to people crossing out of Gaza during a visit to the Egyptian border, and "rarely have I heard such disturbing testimony about the catastrophic harm that ordinary people have endured".

He was unable to access Israel or the Palestinian territories, but stressed Thursday the urgent need for his department to go there, "to ensure full and independent monitoring and documentation, and to coordinate protection work".

He told reporters he had "asked Israel to give me access both to Israel, but also to the occupied Palestinian territory. I have not yet received a response", he said.

The Israeli mission to the UN in Geneva later dismissed his request to visit Israel, telling AFP it "did not see any added benefit of the high commissioner's visit at this time".

During his visit to the region last week, the Israeli mission said Turk had "made it clear that his mind had already been made up, and therefore dialogue with (his office) would contribute little."

- West Bank warning -

During Thursday's briefing, Turk voiced concern about the "intensification of violence and severe discrimination against Palestinians in the occupied West Bank, including East Jerusalem".

"This creates a potentially explosive situation," he said.

"I am ringing the loudest possible alarm bell about the occupied West Bank."

He urged an immediate ceasefire.

"It is apparent that on both sides, some view the killing of civilians as either acceptable collateral damage, or a deliberate and useful weapon of war," he said.

He also insisted that "the Israeli occupation must end".

"Israelis' freedom is inextricably bound up with Palestinians' freedom. Palestinians and Israelis are each others' only hope for peace."

- Israel, Palestinians respond -

Israel harshly criticised UN attempts to balance criticism about violations, insisting that international law was "not a suicide pact".

If a state cannot defend itself "or is criticised for doing so in line with international law, inevitably terrorist organisations will become more and more emboldened," Israeli ambassador Meirav Eilon Shahar told the gathering.

"There is no moral equivalence between Israel and Hamas. We will not let Israel be delegitimised by misrepresentation of reality," she said.

Palestinian ambassador Ibrahim Khraishi flatly rejected that view.

"You should wake up in this room. This is a massacre, this is genocide," he said, accusing Israel of acting "above the law".

"The problem didn't start on October 7 -- It started 75 years ago," he said.

He received support from other countries, including from Jordan's representative who insisted that "Israel must halt its aggression".

US ambassador Michele Taylor meanwhile branded the October 7 Hamas attack as "pure evil", and mourned the Palestinians killed "by the violence resulting from these attacks".

© Agence France-Presse