ITV News Global Security Editor Rohit Kachroo reports, with words by Foreign Producer Natasha Tierney. This report contains distressing details.
When Samer hears the chimes of an ice cream van, he shudders. It forces him to recall one of the darkest moments of his old life in Syria.
We are with him, a long way from Damascus, in the city which he has made his new home - we have agreed not to reveal our location.
But even here, he cannot escape what has become a chilling sound.
“It was an ice cream van, the one that distributes ice cream to shops” he says, recalling the sight, more than a decade ago, of dead bodies being brought in from a military hospital.
Instead of hearses, ice cream vans were used to transport bodies to the site.
This was his old "workplace" – which he would later learn was one of President Bashar al-Assad’s first mass burial sites.
His role there was to dig graves, sometimes under the supervision of intelligence officers.
Samer was ordered to bury them quickly, but often the stray dogs would get there first.
On one occasion, he was told to bury the body of a baby – just days old - killed in detention.
“One van had six corpses from Harasta’s hospital," he says.
"We were told to bury them at once. There were three male corpses, in bags, then three corpses in fabric, in shrouds. They were women. Then there was a baby, no more than 20 or 25 days old. It was also wrapped lightly.”
We look through a pile of satellite images from the area, sprawled across a table in front of us.
Snapshots of several sites, taken over more than a decade, show the evolution of Assad’s mass grave infrastructure.
Samer recognises the precise spot where he once worked and points to it firmly using the very hand that helped to dig the graves.
"We were ordered to dig a hole” he says. “Every time we collected 20 or 30 bodies; we would deliver them into the hole. The first time there was about 75 people.
“A lot of things happened at the time, but this incident left a dent on me, it shocked me to the core.
“This was a child born, surely, at the detention centre, a place that was all about rape.
"The girls were there for the officers when they had their night parties. Those girls were all 15 and 16 years old.
"If, and when they got pregnant, they were killed at once. So here was a child born at a detention centre to become food for dogs. Nothing could be crueler.”
The testimony of eyewitnesses to, and participants, in Assad’s killing machine, shared with ITV News, paint a gruesome picture of the way the Syrian dictator has crushed resistance to his operations.
One witness, who worked for the regime and who has fled within the last few weeks, says the bodies of political prisoners are still being brought from hospitals to be buried in mass graves.
Those claims are supported by analysis of satellite images by ITV News, which show the development of mass grave sites.
At one spot in Najha, a thirty-minute drive from Damascus airport, a civilian cemetery was excavated with new sites dug beneath existing graves to avoid detection from above.
Once it began to fill up, new bodies were brought to another site in Qutayfa, north of the capital, covering an area of around 10 acres.
Trenches and perimeter walls have appeared during the last nine years. But now many bodies are being transferred to a new third site, according to witnesses still working within Assad’s killing machine.
Another man, who we are calling "Rajab", worked at Najha and moved to Qutayfa as the focus of the mass grave operation moved there.
“The smell was overwhelming” he says. “I would stand there with the generals at a distance of 100 or 200 metres.
"Then the youngsters who used to bring the fridges would come closer and I would smell it on them too.
"They talked among themselves about severed arms and limbs. At the end of the day, I just wanted to forget.
"I would just go away, sit in a corner and cry. How could this be?”
His testimony highlights the risks to the hundreds of protestors who have taken to the streets in southern Syria as part of a growing protest movement during the last few days.
What started as small demonstrations over economic corruption and a cut in fuel and gas subsidies, have quickly morphed into a widespread call for the overthrowing of President Assad.
More than 300,000 civilians are believed to have been killed in a bloody civil war waged by their president.
For years outcast from the global stage as a result, recent months have seen President Assad welcomed by some countries back into the diplomatic fold.
In May this year, he attended the Arab League summit in Saudi Arabia, and in three months he is expected to attend this year's COP28 summit on climate change in Dubai.
Opponents fear that Assad’s atrocities are being forgotten and his image is being rehabilitated.
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