Gazans detained by Israeli forces are coming back "completely traumatized" upon release and reporting abuses while in captivity, the head of the UN's Palestinian refugee agency said.

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, AFP reported.

"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.