Syria is facing fresh war crimes allegations after "clear evidence" of the "systematic torture and killing" of up to 11,000 people was published.
The claims were made by a group of top international lawyers, who were handed 55,000 images of dead prisoners.
The lawyers, who are all former war crimes prosecutors, said the photographs showed emaciated corpses with severe injuries and would support findings of crimes against humanity by Bashar al Assad's regime.
Some detainees appeared to have been beaten, strangled or electrocuted, they claimed.
Sir Desmond De Silva, one of the report's co-authors, described the photographs as "very harrowing" and said victims had suffered the "most awful" injuries.

Photos appeared to show Syrian detainees with ligature marks on their necks "These killings were clearly methodical, daily and systematic as a consequence," he told Sky News. "They could certainly underpin a charge of crime against humanity."
He added: "This industrial killing of people in detention is clearly the work of the Syrian government."
The report draws on evidence smuggled out of Syria by an ex-military policeman, known only as Caesar.
He was described as a "truthful and credible witness" by the inquiry team, who said he was "carefully interviewed" and showed "no signs of being sensational".
Caesar told the inquiry team he was asked to take photographs of numbered corpses - a demand that is "wholly consistent with the need of the regime to ensure that orders for the killing of persons in detention facilities had been carried out", according to the report.
Syrian President Bashar al Assad denies his regime has massacred civilians "The need to photograph those who were killed is a strong pointer to the fact that the killings were systematic, ordered and directed from above," it added.
Mr Assad, who describes opponents to his regime as "terrorists", previously rejected claims that his troops have killed civilians.
"These organisations do not have a single document to prove that the Syrian government has committed a massacre against civilians anywhere," he said.
"The army does not shell neighbourhoods. The army strikes areas where there are terrorists."
The report, which was commissioned by Qatar, one of the main supporters of the Syrian opposition, was released the day before crucial peace talks are due to get under way.
Officials from around 40 countries are due to meet in Switzerland, although Iran will not be present after its invitation was withdrawn by the UN.
Mr Hague and Mr Zarif (pictured last year) spoke on the phone on Tuesday After strong objections from the United States and the Syrian opposition, UN Secretary-General Ban Ki-Moon on Monday uninvited Iran, the Damascus regime's main regional ally, less than 24 hours after it was issued.
On the eve of the talks, Foreign Secretary William Hague told Parliament that Mr Ban had been right to withdraw the invitation because of Tehran's refusal to declare its support for a transitional government in Syria.
Mr Hague said Iran's involvement in any future peace settlement would be "extremely important", saying it needed to urgently rethink its Syria policy.
He spoke to Iranian Foreign Minister Javad Zarif on the phone after making his comments, telling him that the idea of brokering a transitional government by mutual consent was the way to end the conflict in Syria and that Britain remained open to working with Iran on that basis in future.
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