The report, which can be found online at both news outlets, relies on the unauthenticated testimony and photographs given by the source, who remains unidentified for security purposes.
The release came yesterday a day before talks were due to be held in Geneva aimed at negotiating an end to Syria's bloody civil war.
The informant, a photographer who claims to have defected from the Syrian military police, presented forensic experts commissioned by the London legal firm representing Qatar with around 55,000 digital images of 11,000 dead detainees.
"Overall there was evidence that a significant number of the deceased were emaciated and a significant minority had been bound and/or beaten with rod-like objects," said the report.
Also Read
The report was written by Desmond de Silva, former chief prosecutor of the special court for Sierra Leone; Geoffrey Nice, the former lead prosecutor in the trial of former Yugoslavian president Slobodan Milosevic; and David Crane, who indicted Liberian president Charles Taylor.
Crane called the evidence "amazing" and suggested there was a strong case for prosecution.
"Now we have direct evidence of what was happening to people who had disappeared," he explained.
"This is the first provable, direct evidence of what has happened to at least 11,000 human beings who have been tortured and executed and apparently disposed of."
The authors said they found the informant and his evidence to be credible after subjecting them to "rigorous scrutiny" and have made their findings available to the United Nations, governments and human rights groups.