Pakistan's army chief has ordered an inquiry into video clips that show men in soldiers' uniforms gunning down a group of bound and blindfolded detainees.
The footage has raised concern over possible extrajudicial killings by a military that receives billions in US aid.
The two clips were apparently shot on mobile phones and have been circulating on the internet. The footage is grainy and shows no time stamps, and part of the army inquiry's mission is to determine whether those shown in uniform were actually soldiers, General Ashfaq Parvez Kayani's statement said.
"It is not expected of a professional army to engage in excesses against the people whom it is trying to guard against the scourge of terrorism," the general said, though he cautioned that militants had in the past posed as soldiers.
It is unclear where the clips were first posted. The SITE Intelligence Group, a US-based organisation that monitors militant websites, reported about two weeks ago they had appeared on an extremist site. The group said they were posted by someone who claimed the footage was from Pakistan's Swat Valley, the scene of a major army offensive against Taliban militants in 2009.
The Pakistani army has been accused of carrying out extrajudicial killings in Swat ever since launching the offensive in May 2009 - allegations it denies. The accusations have concerned American officials who have helped Pakistan gain training and money to improve its fight against al Qaida and the Taliban. US law forbids aid to foreign militaries if they are found to be committing gross violations of human rights.
US Ambassador Anne Patterson spoke to Gen Kayani about the videos when they surfaced and American officials were pleased to learn of the probe, embassy spokesman Richard Snelsire said.
The longer clip lasts five minutes and 39 seconds and shows what appears to be a group of Pakistani soldiers, fully armed and in uniform, guiding the blindfolded men to a wooded area in front of a wall and lining them up next to one another. They are then shot.
A voice is heard saying "finish them one by one". A soldier then walks over to the men and shoots them again. A second clip last 53 seconds and shows only the executions.