Israel is subjecting Gazan detainees to inhumane treatment, including serious abuse, leaving them completely traumatized, according to the U.N. Palestinian refugee agency.

Detainees reported being subjected to a "broad range of ill-treatment" including threats of electrocution, being photographed naked, sleep deprivation and having dogs used to intimidate them, UNRWA chief Philippe Lazzarini told a media briefing Monday.

The comments follow reporting by the New York Times on an internal investigation compiled by UNRWA staff documenting the state of returning detainees at the Kerem Shalom border.

"We have seen these people coming back from detention, some of them for a couple of weeks, some of them for a couple of months, and most of them coming back (are) completely traumatized by the ordeal they have gone through," Lazzarini said.

"A number of people have been ... debriefed about their ordeal, and we have indeed (compiled) an internal report about their experiences."

The report had been shared with rights groups specializing in detention, he added.

Ahead of Lazzarini's comments, meanwhile, UNRWA said Israeli authorities had "detained several of its staff from the Gaza Strip," who later described abuses in custody.

"Our staff have reported atrocious events while they were detained and during interrogations by the Israeli authorities. These reports included torture, severe ill-treatment, abuse and sexual exploitation," UNRWA said in a statement to Agence France-Presse (AFP).

"Some of our staff have conveyed to UNRWA teams that they were forced to sign confessions under torture and ill-treatment" while being asked about Hamas's Oct. 7 incursion.

The "IDF denies general and unsubstantiated claims regarding sexual abuse of detainees in the IDF's detention facilities," the Israeli military said in a statement, using the abbreviation for the Israeli Defense Forces.