A list of 20 sample war crimes indictments of Syrian government officials and rebels has placed President Bashar al-Assad in the top spot, a former international war crimes prosecutor said.
"We have about 20 indictments of those who bear the greatest responsibility. This is a neutral effort. We're not just going after Assad and his henchman, we are actually documenting all incidents on both sides," David Crane, an ex-chief prosecutor of the Special Court for Sierra Leone and now head of the Syria Accountability Project told Reuters news agency.
The International Criminal Court has been handed the list, citing for each incident a specific violation of the Rome statute under which a suspect could be charged, Al Arabiya reported.
The list, which included members of Syria's military and political elite plus Islamist rebel groups ISIS and al-Nusra Front, was compiled by Crane's expert group.
However, only Assad's name was revealed by Crane.
Images taken by a Syrian military police photographer codenamed Caesar, published in January, supplied "clear evidence" showing the systematic torture and killing of about 11,000 detainees in conditions that evoked Nazi death camps, former prosecutors including Crane have said.
"We rarely get this type of evidence, most of it is circumstantial," Crane said of the 55,000 photographs of bodies, many with gouged-out eyes and bearing signs of starvation.
"Make no mistake about it, these photographs could not be faked. This takes responsibility for what happened up the ladder of responsibility. It is not an act of a maverick colonel or a mad major, this is government policy," said Sir Desmond de Silva, co-author of an analysis of the "Caesar" photos and another former Sierra Leone chief prosecutor, told the panel.
A six-week offensive by ISIS against rival Islamists in eastern Syria has killed 600 fighters and driven 130,000 people from their homes, a London-based monitoring group said on Tuesday.