More than 150 Syrian soldiers were stripped and marched into the desert to be shot by Islamic State militants, activists have claimed.
A video has been posted to YouTube purporting to show the men, who are barefoot and in their underwear, being escorted into the desert.
It then goes black before revealing a similar number of men, also in their underwear, lying dead in the sand.
The video has yet to be verified but correspond to other reports from the region, and tie up with a statement and claims made via Twitter relating to the mass killing of troops captured in recent fighting for a string of military bases in north-eastern Syria.
There has been no immediate comment from the Syrian government.
More top news
NASA has given the green light to an emergency space walk to repair a broken-down computer attached to the International Space Station.
A necklace blessed by Buddhists helped a British woman become the youngest female to scale Mount Everest from both sides, she claims.
Celebrities including Leonardo DiCaprio have holidayed there - and even former US President Barack Obama is a fan.