The Pakistani military says it is investigating a video purporting to show a firing squad of uniformed soldiers shooting dead young men who were blindfolded and bound.
Its authenticity cannot be verified. It is unclear when or where it was filmed.
Human rights groups say they have previously documented extra-judicial killings by Pakistani troops but cannot vouch for the video.
Pakistani military officials have dismissed it as fabricated.
"No Pakistani Army soldier or officer has been involved in activity of this sort," army spokesman Maj Gen Athar Abbas told the BBC.
US voices concernThe individual who sent it to the BBC said many people in the Swat valley had the clip on their phones.
However journalists in Swat have told the BBC that the first they heard of the video was when it was reported in the New York Times two days ago.
It shows men in military clothing pushing a group of young men one by one through a forest.
BBC News
