Syrian and international delegates were arriving in Switzerland yesterday on the eve of peace talks that few believe can succeed as the three-year-old civil war and geopolitical acrimony it has brought show no sign of abating.

Opponents of President Bashar al-Assad, pressured to attend today’s first direct negotiations by their Western backers, cited new, photographic evidence of widespread torture and killing by Syria’s government in renewing their demand that Assad must quit and face an international war crimes trial.

War crimes lawyers said a vast, smuggled cache of images from a Syrian military police photographer gave clear evidence of systematic abuse and murder of some 11,000 detainees. One of three former international war crimes prosecutors who signed the report compared the images from Syria to the “industrial-scale killing” of Nazi death camps.

The delegation from Damascus, led by Assad’s foreign minister, was briefly held up at Athens due to an argument over whether EU trade sanctions permitted refuelling the plane.

Assad has insisted he may be re-elected and says the talks should focus on fighting “terrorism” – his term for his enemies.

The United Nations, along with co-sponsors Russia and the US, may at least be relieved if and when the two sides sit down at the Montreux Palace hotel on Lake Geneva.

A day of diplomatic chaos on Monday had threatened to scupper the event entirely, after UN Secretary-General Ban Ki-moon gave a last-minute invite to Iran, Assad’s main foreign supporter.

The invitation was withdrawn after a boycott threat from the opposition, Western pressure and Iran’s insistence it had never agreed to the condition Ban set for attendance – that it endorse a previous peace conference, at Geneva in 2012, which called for Assad to make way for a transitional administration.

Narrowing the gap between the warring parties seems a tall order and diplomats at the UN stress the meeting at Montreux today, to be followed possibly by further talks in Geneva from Friday, is only a beginning. It could produce deals to ease civilian suffering and exchange prisoners.

Not only are both sides committed to a fight on the frontlines, where victory continues to elude either party, but most of the myriad rebel groups have disowned the National Coalition opposition group for agreeing to talk.

The bodies he photographed since the civil war began showed signs of starvation, brutal beatings, strangulation and other forms of torture and killing. In some cases they had no eyes

The spread of violence, which has already killed more than 130,000 and driven a third of Syria’s 22 million people from their homes, has given a new, common impetus to international efforts to end the bloodshed.

The bleak consequences of the war were illustrated starkly in photographs of detainees’ emaciated and abused bodies, released in a report commissioned by London law firm Carter-Ruck, hired by Qatar, a supporter of Assad’s foes.

The report, by three senior lawyers who have worked for international war crimes tribunals and three forensic experts, said they believed the pictures and the photographer’s account were credible evidence Assad’s government had systematically tortured and killed as many as 11,000 detainees.

They said they had been shown 55,000 images, most of which were provided by a source who identified himself as a Syrian police photographer whose job included documenting deaths in Assad’s jails on behalf of the authorities.

The man, who sometimes photographed 50 bodies a day, had defected with digital copies.

“The bodies he photographed since the civil war began showed signs of starvation, brutal beatings, strangulation and other forms of torture and killing,” the lawyers wrote. “In some cases the bodies had no eyes.”

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.