War crimes investigators and activists have amassed an "overwhelming volume" of testimonies, images and videos documenting atrocities committed by all sides during Syria's war, a U.N. quasi-prosecutorial body said in its first report.

The team, led by former French judge Catherine Marchi-Uhel, said it is preparing case files and has engaged with war crimes investigative units from various states, including in Europe, whose courts can exercise universal jurisdiction to prosecute.

In the future, an existing body — such as the International Criminal Court — or a new court could be given jurisdiction for Syria, according to the report.