At least 100,000 bodies of victims of the Assad regime in a mass grave near Damascus

He told Reuters that in Al Qutaifah, 40 kilometers north of Damascus, there is one of the five mass graves.

"One hundred thousand is the most conservative estimate" of the number of bodies buried at the site, Mustafa said.

He believes, as he notes, that there are more than five mass graves, and that among the victims were US and British citizens, as well as other foreigners.

Mustafa said the intelligence branch of the Syrian Air Force was "in charge of transferring bodies from military hospitals, where the bodies were collected after (people) were tortured to death, and then they would be sent to the mass grave site."

As he noted, the bodies were also transported to the graves by the municipal funeral office in Damascus, whose staff helped unload the victims from the refrigerators from the tractor trailers.

According to him, SETF personnel spoke with bulldozer drivers who, they claim, were forced to dig graves and "many times were ordered to crush the bodies to fit them and then cover them with earth," according to Reuters.

Mustafa also expressed concern that the graves were not secured and pointed out that it is important to preserve them in order to preserve evidence for investigations.

Hundreds of thousands of Syrians are estimated to have been killed since the country's civil war broke out in 2011, while Assad has repeatedly denied that his government has violated human rights.