DAMASCUS, Syria, Feb. 8 (UPI) -- The United Nations Human Rights Council said it has uncovered evidence of rampant and gruesome violence committed against Syrian detainees by the regime of President Bashar al-Assad over a period of four years as the nation's civil war dragged on.
The council began the investigation following reports of widespread abuse, torture and the killings of Syrian detainees since the start of the civil war in 2011. Between then and 2015, investigators say, extensive evidence supports conclusions that Assad's regime repeatedly committed an untold number of human rights violations.
The Human Rights Council's report, titled "Out of Sight, Out of Mind: Deaths in Detention in the Syrian Arab Republic," details dozens of incidents based on interviews with more than 600 people -- most of whom are former detainees and eyewitnesses to the reported atrocities, the council said.
"Massive and systematised violence -- including the killing of detainees in official and makeshift detention centres -- has taken place out of sight, far from the battlefield," the report says in its introduction.
"The [Syrian] government has committed the crimes against humanity of extermination, murder, rape or other forms of sexual violence, torture, imprisonment, enforced disappearance and other inhuman acts," it continues.
Perhaps one of the most shocking allegations made by the Human Rights Council is that government forces killed women and children -- as young as 7 -- in the course of the state's interrogation protocols.
"One of the earliest documented cases of death in detention is that of a 13-year-old boy, arrested during a protest in Sayda [Dara'a] in late April 2011," the Human Rights Council report said. "His mutilated body was returned to his family in May 2011. Women, boys and girls, as well as the elderly, have been subjected to torture and brutal prison conditions and have suffered physical and mental trauma. They too have been the victims of, as well as witnesses to, deaths in custody."
The report also details a male detainee's death in 2014, before which he was beaten during torturous interrogations.
"The victim was left vomiting blood. A former cellmate explained how the man asked him to tell his wife and family what happened to him," the report says.
"He died. We closed his eyes, wrapped him in a military blanket and read the Koran in our hearts," the cellmate told investigators.
Other instances of abuse include the burning of an elderly man's eyes with cigarettes and mutilation of one's genitals during interrogation. In each case, it took the detainee three days to die, the report found.
The council's report also says that at no time were any of the detainees given medical treatment after interrogation. Also, some abuses were sexual in nature.
"Many detainees were subjected to rape and other forms of sexual violence, and exposed to humiliation and degrading treatment. Prisoners were subjected to threats of sexual violence against female relatives," the report states.
Investigators also cited deplorable prison conditions, "including severe over-crowding, lack of food, and unclean drinking water," that also led to detainee deaths.
"Prisoners were given inadequate or no medical care, and died in large numbers from preventable conditions such as diarrhea or other contagious infections spread in the unhygienic and overcrowded cells," the report says.
The report alleges Assad's government consequently undertook great efforts to cover up the abuses. In some cases, state forces returned the victims' bodies to relatives and required the families to sign statements saying the detainees had been killed by "terrorists."
The United States and other international bodies have suspected human rights abuses in Syria for years -- particularly recently, as the civil war has persisted under Assad's leadership and has resulted in hundreds of thousands of deaths. Some estimate the death toll has surpassed a quarter million people.
Assad, though, isn't the only party accused in the report. Militant groups the Islamic State -- also identified as Daesh, ISIS and ISIL -- and al-Qaida affiliate al-Nusra also are accused of committing numerous human rights violations and war crimes, as well.
"Detainees held by the government were beaten to death, or died as a result of injuries sustained due to torture. Others perished as a consequence of inhuman living conditions," the report says. "ISIS subjected detainees to serious abuses, including torture and summary executions. Detainees were frequently executed after unauthorised courts issued a death sentence.
"The situation of detainees is critical, and represents an urgent and large-scale crisis of human rights protection."
"Many parties to the Syrian conflict have committed serious violations of the rights of detainees, including the right to life," the U.N. report says in its conclusion.
"It is apparent that the government authorities administering prisons and detention centres were aware that deaths on a massive scale were occurring. ... There are reasonable grounds to believe that the conduct described amounts to extermination as a crime against humanity. ... the government has committed the war crimes of murder, cruel treatment, torture, rape, sexual violence, and outrages upon personal dignity."
The United States has sternly condemned Assad for years -- accusing him in a wide spectrum of abuses and rejecting out of hand any peace agreement that leaves him in power. Russia, meanwhile, has remained Assad's most valuable ally in the international community -- which has only served to deepen the diplomatic tension between Washington and Moscow.
The Human Rights Council report, issued Feb. 3, comes as the UN is trying to facilitate a peace agreement to end the Syrian civil war. Assad's regime and opposition figures met last week in Switzerland to continue discussions brokered by special envoy Staffan de Mistura, but the talks were halted amid escalating violence in Aleppo, Syria.
The peace talks were scheduled to resume Feb. 25.