Syrian officials could face war crimes charges based on photographs from a defector proving the “industrial-scale” torture and killing of 11,000 detainees by the regime, international prosecutors say.

Evidence smuggled out by a former Syrian military police photographer was reminiscent of the conditions in the death camps in Nazi Germany in World War II, the three investigators said on Tuesday.

A report by the prosecutors – commissioned by Qatar, which backs the Syrian rebels – provides “clear evidence” of the starvation, strangulation and beating of detainees in President Bashar al-Assad’s prisons.

The release of the report, which was first revealed by The Guardian newspaper, CNN and Turkey’s Anatolia news agency, comes a day before talks are due to begin in Geneva aimed at negotiating an end to Syria’s bloody civil war.

“There is clear evidence, capable of being believed by a tribunal of fact in a court of law, of systematic torture and killing of detained persons by the agents of the Syrian government,” the report said.

“Such evidence would support findings of crimes against humanity against the current Syrian regime. Such evidence could also support findings of war crimes against the current Syrian regime.”

Syria has previously denied torturing detainees but the government had no immediate reaction to the report.

British Foreign Secretary William Hague said the report “offers further evidence of the systematic violence and brutality being visited upon the people of Syria by the Assad regime”.

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.

It also features testimony from a forensic pathologist, an anthropologist who investigated mass graves in Kosovo and an expert in digital images.

The defector, identified only as “Caesar” for his own safety, presented forensic experts commissioned by a London legal firm representing Qatar with around 55,000 digital images of 11,000 dead detainees since the start of the uprising in Syria in March 2011. The images were on memory sticks.

He claims the victims all died in captivity before being taken to a military hospital to be photographed.

The report says that all but one of the victims were male. Most appeared to be aged between 20 and 40.

The defector photographed as many as 50 bodies a day, the report said.