Prisoners in a police station loyal to the Free Syrian Army rebel group near Damascus in May 2014.

China Stringer Network / Reuters

Thousands of Syrians have died in squalid prisons during more than four years of civil war in the country, according to a United Nations report released Monday, with men, women, and children subjected to horrific torture by both regime and anti-government fighters.

The U.N. Commission of Inquiry on Syria found government officials have committed "vast state resources" to the systematic "extermination" of detainees. The commission, a subset of the Human Rights Council, directly accused the government of President Bashar al-Assad of crimes against humanity.

Since fighting broke out in the country in 2011, thousands of Syrians — mostly males older than 15 — have been arbitrarily arrested and imprisoned by the regime, the U.N. found. "Former detainees detailed how cellmates were killed as they were beaten to death during interrogations and in their cells, or died as a result of severe injuries sustained due to torture or ill treatment," the report reads.

One prisoner died from severe bleeding after his genitals were mutilated during torture, the report found, while another man only died after he was hung by his wrists for several hours, had his eyes burnt with a cigarette, and had his body pierced with a hot metal object.

The Commission also found prisons were intentionally kept in poor condition by officials with the intent of causing detainees to die. "Others perished as a consequence of inhuman living conditions inflicted on the prison population, including severe over crowding, lack of food, and unclean drinking water," the report reads.

Many prisoners have been executed without proper trials, often relying on supposed evidence induced through torture, according to the report. In January 2013, more than 140 bodies were found floating in a river in a government-controlled area in Aleppo, many of which were found with their hands tied behind backs and with evidence of gunshot wounds.

An ISIS prison in Tal Abyad, Syria.

Ahmet Sik

Anti-government forces, including jihadist groups like ISIS and Jabhat Al-Nusra, have also systematically tortured and killed prisoners, but the U.N. found these captives were mainly captured government fighters.

"No institutionalized or consistent practice of mass arrests and arbitrary detention, torture, and killing of detained civilians in areas controlled by most of these groups has been documented," the report found.

The inquiry did find, however, a number of instances where civilians, including reporters and even young children, were tortured and killed by the jihadist groups.

In addition to a number of recommendations aimed at the Syrian authorities and anti-government groups, the U.N. commission called on the Security Council and the broader international community to adopt targeted sanctions against those credibly suspected of torture.

“The situation of detainees in Syria is critical, and represents an urgent and large-scale crisis of human rights protection,” Commissioner Vitit Muntarbhorn said in a statement. “With thousands of persons still in custody, urgent steps need to be taken by the Syrian Government, armed groups, the external backers of various belligerents, and the wider international community to prevent further deaths”.

Read the U.N. report here:

LINK: Life And Death Inside An ISIS Prison