Expanding Israeli settlements in the occupied Palestinian territories constitutes "a war crime" and risks eliminating any likelihood of a viable Palestinian state, the UN rights chief warned on Friday.

Volker Turk said there had been a drastic acceleration in Israeli illegal settlement building in the occupied West Bank as it wages a relentless war in the Palestinian territory of Gaza.

The UN high commissioner for human rights said creating and expanding settlements amounted to the transfer by Israel of its own civilian population into occupied territories.

"Such transfers amount to a war crime that may engage the individual criminal responsibility of those involved," Turk said in a report to the UN Human Rights Council.

Reported Israeli plans to build another 3,476 settler homes in the West Bank colonies of Maale Adumim, Efrat and Kedar "fly in the face of international law", he said.

Spain echoed the sentiment on Friday, with its foreign ministry saying it "strongly condemns" the planned settlements that "undermine efforts to achieve a two-state solution and are an obstacle to peace".

France's foreign ministry also said it "strongly condemns" the settlement plan and called on the Israeli government to "immediately reverse this decision".

Israel seized the West Bank, east Jerusalem and the Gaza Strip in the 1967 Arab-Israeli war.

It is illegal under international law for Israel to establish settlements in those Palestinian territories.

Despite opposition abroad, Israel has built dozens of settlements across the West Bank in recent decades.

They are home to more than 490,000 Israelis, living in the same territory as around three million Palestinians.

Israel gave the go-ahead for the new homes less than two weeks after US Secretary of State Antony Blinken said any settlement expansion would be "counterproductive to reaching enduring peace" with the Palestinians.

- Violence concerns -

Turk said that during the period covered by his report -- November 1, 2022, to October 31, 2023 -- some 24,300 housing units were added to existing Israeli settlements in the West Bank.

That marks the largest number on record since monitoring began in 2017. It includes nearly 9,700 units in east Jerusalem, the UN rights office said.

Turk's report found that the Israeli government's policies "appear aligned, to an unprecedented extent, with the goals of the Israeli settler movement to expand long-term control over the West Bank, including east Jerusalem, and to steadily integrate this occupied territory into the State of Israel".

At the same time, Palestinians are being forced from their homes by Israeli settler and state violence, it said.

It also pointed to forced evictions, non-issuance of building permits, home demolitions and movement restrictions imposed on Palestinians.

It found there had been 602 settler attacks against Palestinians since October 7, the date of Hamas's attack inside Israel, leading to the war in Gaza.

The UN rights office said it had documented nine Palestinians killed by West Bank settlers using firearms, and another 396 killed by Israeli security forces.

Two others were killed by either Israeli security forces or settlers.

In response, Israel's mission in Geneva said Turk and his office had "once again totally ignored the deaths of 36 Israelis, including women and children and one tourist, and the 296 injured as a result of Palestinian terrorism in 2023, before and after October 7.

"Human rights are universal, yet Israeli victims of Palestinian terrorism are ignored by the office time and time again," the Israeli mission said.