Syrian men and boys, in their war-torn country and abroad, have suffered "a vicious cycle" of sexual abuse with more devastating consequences than previously reported, the United Nations said Thursday.

In its new report, "We Keep it in our Heart," the UN's refugee agency said it had documented widespread sexual violence against Syrian males, including those seeking refuge.

"There have been documented reports of how Syrian women and girls have suffered sexual violence and displacement. However, this particular issue is a lesser known element of this grim story -- the male survivors, the boy survivors," said UNHCR spokesman Andrej Mahecic.

"The results are clear. There is a vicious cycle here," he told AFP.

Based on input from 196 refugees and interviews with 73 humanitarian personnel, the report says sexual abuse has been a "disturbing" feature of Syria's nearly seven-year conflict.

Men and boys have suffered sexual violence in detention centres and checkpoints manned by armed factions -- but also in countries hosting them as refugees.

"One of my uncles in Syria was arrested. A few months after he was released from detention, he told us -- he broke down, crying in front of us -- that there was not one spot on his body that had not been abused by an electric drill," said Ahmed, a Syrian refugee in Jordan.

"After he was released he stopped eating and became alcoholic. He died from kidney failure."

Gay, bisexual, transgender, and intersex Syrians were especially vulnerable.

"There's no one (in the LGBTI refugee community) that didn't go through sexual violence. It's something that happens to everyone, to all of us," said Mazen, a young transgender man cited in the report.

Forms of sexual violence included electric shocks, cigarette burns to the genitals and anus, castration, and gang rape.

And in countries of asylum, Syrian men and boys reported being blackmailed into sexual relationships or exploited by employers.

The UN said the abuse impacted entire families and led to "profoundly debilitating and destabilising psychological consequences".

Boy survivors at times quit school, and were -- along with men -- shunned and shamed, and even threatened with death.

Survivors also were afraid of social stigma if they came forward, and humanitarian service providers were sometimes short-staffed or dismissive of male claims.

"Victims refrain from approaching services and they blame themselves. This reinforces the myth that this is a rare problem, while this study shows the opposite," said Mahecic.