The Islamic State, otherwise known as ISIS or Daesh, released a new video showing the mass execution of over 20 soldiers at the ruins of the ancient city of Palmyra in Syria on Saturday.

Stills of the video started circulating through Twitter on Saturday morning showing 25 captured men kneeling inside the amphitheater of Palmyra in front of a crowd of men while the black banner of ISIS hangs behind them. The executioners shoot the men in the head while the audience watch.

Both SITE Intel Group, an Islamic terrorism watchdog, and independent groups such as Raqqa is Being Slaughtered Silently have both confirmed the video and uploaded photos to Twitter.

According to Agence France-Presse, the video appears to have been recorded on May 21, following ISIS takeover of the ancient site and the surrounding cities. The Syrian Observatory of Human Rights first reported the execution on May 27.

“Using the Roman theatre to execute people proves that these people are against humanity," Syria's antiquities director Mamoun Abdelkarim told the AFP.

The ancient ruins are considered a UNESCO World Heritage Site and have stood there for millennia. When ISIS first took over the city, many around the world feared the group would destroy it in the same fashion it has destroyed other ancient cities throughout Syria and Iraq.

This is the most recent video released by the group, following a video in June in which prisoners, donning the now infamous orange jumpsuits, were execution in various manners.

Saturday’s video is the first one in which the prisoners -- Syrian soldiers captured at Holms, according to the BBC -- were not wearing the orange outfits.