GENEVA (AP) — The U.N. human rights office issued a report Wednesday saying Palestinians detained by Israeli authorities since the Oct. 7 attacks faced waterboarding, sleep deprivation, electric shocks, dogs set on them, and other forms of torture and mistreatment.

The report said Israel's prison service held more than 9,400 "security detainees" as of the end of June, and some have been held in secret without access to lawyers or respect for their legal rights.

A summary of the report, based on interviews with former detainees and other sources, decried a "staggering" number of detainees — including men, women, children, journalists and human rights defenders — and said such practices raise concerns about arbitrary detention.

"The testimonies gathered by my office and other entities indicate a range of appalling acts, such as waterboarding and the release of dogs on detainees, amongst other acts, in flagrant violation of international human rights law and international humanitarian law," said U.N. Human Rights Chief Volker Türk in a statement.

Findings in the report, one of the most extensive of its kind, could be used by International Criminal Court prosecutors who are looking into crimes committed in connection with Hamas' Oct. 7 attacks and Israel's blistering ongoing military campaign in Gaza.

In May, the ICC's chief prosecutor sought arrest warrants for leaders of Israel and Hamas, including Israeli Prime Minister Benjamin Netanyahu, over war crimes and crimes against humanity in the Gaza Strip and Israel.

Authors of the report said its content was shared with the Israeli government.

In response to the report, the Israeli military said that abuse of detainees was illegal and against military orders. It said since the war began there have been cases where correctional staff have been dismissed for violating military rules in their treatment of detainees. Investigations are launched into all detainee deaths in custody, it said.

Israel's Prison services did not respond to an Associated Press request for comment.

Israel's prison authorities previously told the AP that all Palestinian prisoners are treated according to Israeli law. However, Israel's Ministry of National Security, the body in charge of prisons, says it has actively made conditions worse and purposefully overcrowded cells for Palestinians held on security charges since the war broke out as a policy of deterrence.

The ministry is headed by ultranationalist minister Itamar Ben Gvir, who has long called for harsher punishment, including the death penalty, for Palestinians held on terror charges.

The report also said detainees were taken from Gaza, Israel and the West Bank, and says Israel has not provided information regarding the fate or whereabouts of many, adding that the International Committee of the Red Cross has been denied access to facilities where they are held.

"Detainees said they were held in cage-like facilities, stripped naked for prolonged periods, wearing only diapers. Their testimonies told of prolonged blindfolding, deprivation of food, sleep and water, and being subjected to electric shocks and being burnt with cigarettes," a summary of the report said.

"Some detainees said dogs were released on them, and others said they were subjected to waterboarding, or that their hands were tied and they were suspended from the ceiling," it added. "Some women and men also spoke of sexual and gender-based violence."

The report said the Palestinian Authority, which administers parts of the Israeli-occupied West Bank, had also "continued to carry out arbitrary detention and torture or other ill-treatment in the West Bank, reportedly principally to suppress criticism and political opposition."

On Wednesday, an Israeli military court extended the detention of eight out of nine soldiers being held over what a defense lawyer said were allegations of sexual abuse of a Palestinian at Sde Teiman — a shadowy facility where Israel has held prisoners from Gaza during the war. The soldiers' detention triggered angry protests by supporters demanding their release.

The war in Gaza erupted after Hamas ' surprise attack on southern Israel on Oct. 7, killing some 1,200 people that day and taking 250 others hostage. Israel's retaliatory operation has obliterated entire neighborhoods in Gaza and forced some 80% of the population to flee their homes. Over 39,000 Palestinians have been killed, according to Gaza's Health Ministry which doesn't distinguish between civilians and combatants in its count.

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Associated Press writer Jack Jeffery contributed to this report from Ramallah, West Bank.