GENEVA >> 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, 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.