Men ordered to rape each other to 'amuse' a sick guard. Women raped in front of family members to force confessions. And blood - rivers of blood from the sustained beatings and torture.

This is from the testimony of 65 former prisoners in Assad's jails across Syria who have spoken out about the horrendous conditions they endured in order to give a voice to those left behind.

Denied access to government prisons in Syria, Amnesty International has compiled an in depth investigation into human rights abuses inside military jails across the war torn country.

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Brave: Former prisoners have come forward to reveal the abuse they suffered in Assad's prisons. Above, Anas Hamoud

Torture: One torture method described by survivors involves being forced to through a tyre while being beaten

Cramped: Survivors recalled having to sleep 'like knives', packed into overcrowded cells where inmates would frequently die and bodies would be collected each morning

While the horrific abuse has been documented in ISIS and rebel detention centres, the sheer scale of systematic human rights violations are being carried out by the Syrian army

While the horrific abuse has been documented in ISIS and rebel detention centres, the sheer scale of systematic human rights violations are being carried out by the Syrian army, according to the watchdog.

The organisation estimates that more than 17,723 people have died in custody in Syria over the past five years - an average of more than 300 people each month, about 10 a day.

Amnesty's 69-page report documents the testimony of men and women subjected to electrocutions, beatings, stress positions, rape, severe cold and the withholding of medical treatment, food, and water.

Other torture methods include being crushed for hours while being beaten with sticks

All survivors described being subjected to a 'Welcome Party', where they were beaten by guards the moment they arrived at the prison, or were moved to a different location

Shackled: Testimony includes descriptions of being hung by the wrists for hours while beaten by guards. Inmates learned to massage each others arms after the abuse to restart the circulation and to stop them losing their limbs

Researchers have also compiled a 3D impression of what the inside of the notorious Saydnaya Prison looks like through satellite imagery and memories of those who were detained there.

One survivor, named only as Omar S, recounts being made to watch a prisoner being forced to rape another.

'Because of our situation – we look very bad, and we smell bad – so the guards wouldn’t usually make any sexual advances on us. But still, there was one time that the guard stripped all of us. And he chose two of us, one of us huge, and the other very small.

'He told the two to come to him. He asked them to turn in a circle, to show him their bodies. Then he ordered the bigger one to rape the smaller one. Because of the torture, and the situation, he couldn’t, even if he had tried. The guard told him he had to do it or he would die.'

Former detainees from the intelligence branches have described being held in cells so overcrowded they had to take turns to sleep, or had to sleep while squatting saying 'it was like being in a room of dead people'.

'They were trying to finish us there,' said Jalal, a former detainee. Another detainee, 'Ziad' (not his real name), said the ventilation in Military Intelligence Branch 235 in Damascus stopped working one day and seven people died of suffocation:

'They began to kick us to see who was alive and who wasn't. They told me and the other survivor to stand up ... that is when I realised that ... seven people had died, that I had slept next to seven bodies … [then] I saw the rest of the bodies in the corridor, around 25 other bodies.'

Recreation: Amnesty Researchers used testimony and satellite imagery to create a 3D version of the most brutal and notorious military prison north of Damascus - Saydnaya

Researchers have made the interactive 'tour' of the prison complete with the sounds heard by the prisoners

Despite President Assad inviting an 'unbiased and fair' investigation into allegations of torture and other ill-treatment, Amnesty were denied both access or a specific response to the allegations

Farhan is an IT professional from Homs. He was helping to organize peaceful demonstrations and provide humanitarian goods for civilians in hard–to-reach areas when he was arrested in March 2012.

He was detained for a week at the local General Intelligence branch in Homs before being moved to Military Intelligence Branch 235 in Damascus and was eventually released in November 2013.

During the first week at the local General Intelligence branch, he explained: 'My cellmate died… He was resting on my leg, after he had been tortured… He was dead on my leg. He had two daughters, and he told me this right before he died. I knocked on the door to tell them I had a dead person in the cell. They said, "He's not a person. He's just a body, a corpse."

Amnesty International's Middle East and North Africa Director Philip Luther said the report showed every stage of their ordeal

'When they took me inside the prison, I could smell the torture. It’s a particular smell of humidity, blood and sweat; it’s the torture smell,' Salam told Amnesty researchers

'It was a very small room – a solitary cell. He was there with me for three days. I will never forget the smell. He had holes all over his body. He wasn't thin. He had kept his health, unlike a lot of the other prisoners… The skin and flesh just under his eye were missing.

They took the electroshock device and inserted it into my anus and switched it on. One of the guards asked for my face to be uncovered and I saw my father. He had witnessed all of it. Said, arrested 2011 in Aleppo

The guard came and said, "It's obvious you still care about this body, so you can carry it." I had to carry the body down the hallway, and I reached what looked to be a mountain of bodies. There were six or seven bodies there, and a couple had military uniforms on, but most of them were in civilian clothes. I tripped when I got there, and fell into the bodies.'

Prior to his arrest, Said was an activist calling for democratic change in Syria. He was arrested by Military Intelligence agents in Aleppo in 2011.

He described one of his interrogations: 'All of this time I was blindfolded. I was hung from my left hand, my shoulder was dislocated. I lost the feeling in my hand… While I was hanging in the shabeh position with one hand, they used an electroshock baton to hit my penis.

'Then they took the electroshock device and inserted it into my anus and switched it on. This was my first experience of rape. Then one of the guards asked for my face to be uncovered and I saw my father there. He had witnessed all of it.

The accounts seem to tie in with testimony and photographs delivered by 'Caesar', a Syrian military defector who smuggled d 53,275 photographs out of the country

At least 6,786 of 'Caesar's' photographs showed victims who had died either in prisons or military hospital, according to Human Rights Watch

Most of the 6,786 victims shown in the Caesar photographs were detained by just five intelligence agency branches in Damascus

Amnesty International's Middle East and North Africa Director Philip Luther said the report showed every stage of their ordeal - from the moment of their arrest, through their interrogation and detention behind the closed doors of Syria's notorious intelligence facilities.

While torture has been alleged as being inflicted on prisoners for decades in Syria, Mr Luther said the computerized version of the prison gives for the first time a 'true glimpse' of the horror.

'Using 3D modelling techniques and the memories of those who survived horrendous abuse there, for the first time we are able to get a true glimpse inside one of Syria's most notorious torture prisons,' he said.

The accounts seem to tie in with testimony and photographs delivered by 'Caesar', a Syrian military defector who smuggled d 53,275 photographs out of the country and were examined by Human Rights Watch among others.

At least 6,786 photographs showed victims who had died either in prisons or military hospital, according to Human Rights Watch.