ISIS video shows execution of 25 men in ruins of Syria amphitheater

A just-released video from ISIS shows militants executing 25 captives in the ruins of a Roman amphitheater in the ancient Syrian city of Palmyra.

The graphic video begins with images of the Quran, followed by gruesome scenes showing what appears to be the aftermath of fighting, with bodies in the street. Then it shows captives, heads down and dressed in dark fatigues, as they are herded single-file onto the stage of an ancient arena. A row of young men, many appearing to be in their teens, stands behind the prisoners while an older man reads a document to the assembled crowd.

Periodically, the video shows men seated on the crumbling stone seats. Some are waving ISIS flags, but others appear distressed, hiding their faces and even crying.

When the cue is given, the young militants shoot the assembled captives all at once. The scene includes an editing trick which runs the film in reverse, making the deceased appear to rise and get shot again.

CNN could not independently confirm the authenticity of the recording.

The video is approximately 10 minutes long and is undated. According to the British-based Syrian Observatory for Human Rights, which received a copy of the video, the execution occurred on May 27, shortly after ISIS fighters took over the ancient city.

The video also shows militants blowing up the notorious Tadmur prison, which was used to house political prisoners in Syria, during the regimes of President Bashar al-Assad and his father, President Hafez al-Assad. A 2001 report from Amnesty Inteational called conditions at the facility "brutal and dehumanizing.”

The ISIS video shows prison cells and boxes of files, followed by ISIS fighters rigging the grounds with explosives. A masked militant is shown pushing a detonator. Then several images of the explosion are shown, once again featuring special editing effects.