An international war crimes prosecutor said on Tuesday that evidence emerging from mass grave sites in Syria has exposed a state-run “machinery of death” under toppled leader Bashar al-Assad in which he estimated more than 100,000 people were tortured and murdered since 2013. Speaking after visiting two mass grave sites in the towns of Qutayfah and Najha near Damascus, former U.S. war crimes ambassador at large Stephen Rapp told Reuters: “We certainly have more than 100,000 people that were disappeared into and tortured to death in this machine. “I don’t have much doubt about those kinds of numbers given what we’ve seen in these mass graves.” “We really haven’t seen anything quite like this since the Nazis,” said Rapp, who led prosecutions at the Rwanda and Sierra Leone war crimes tribunals and is working with Syrian civil society to document war crimes evidence and is helping to prepare for any eventual trials. “From the secret police who disappeared people from their streets and homes, to the jailers and interrogators who starved and tortured them to death, to the truck drivers and bulldozer drivers who hid their bodies, thousands of people were working in this system of killing,” Rapp said. “We are talking about a system of state terror, which became a machinery of death.” Hundreds of thousands of Syrians are estimated to have been killed since 2011, when Assad’s crackdown on protests against him spiralled into a full-scale war. Both Assad and his father Hafez, who preceded him as president and died in 2000, have long been accused by rights groups and governments of widespread extrajudicial killings, including mass executions within the country’s prison system and using chemical weapons against the Syrian people.