Transcript for 'Dirty Brigades': US-Trained Iraqi Forces Investigated for War Crimes
Innocent civilians massacred. Prisoners torture. Acts that shocked the civilized world. All discovered by ABC news online. Not from the usual ices accounts but on social media sites connected to elite units of the Iraqi Army. The very forces the US is counting on to help stop such atrocities. Peer group of men in Iraqi Army uniform. And a sign of approval after a civilian is be headed behind. In this a young boy I suspected I since recruit Obama is about to be executed shot dead in the street. With men in what appeared on the Iraqi uniforms crowding around the scene. This appears to be an insignia of the Iraqi special forces. Hmmm what we're seeing here is a brazen proud display of these terrible crimes. There are dozens of such videos and still images now being investigated by US and Iraqi authorities to determine if they are in fact. Part of the Iraqi Army. Like these men with a severed head. Are these men drinking the body of a captured prisoner. In this video what appeared to be two on armed Iraqi civilians are about to be murders like the others already dead next to. This video slowed down shows militia fighters with US supplied weapons. This freeze frame catches a soldier would let experts say is another insignia for the special forces witnessing without stopping what is about to happen. The prisoners say they are just villagers crisis. As he begs for his life he has asked did you steal them did you see them. And we won't show the horrifying thought. After a few minutes to civilians are shot and killed anyway. And then the other men opened fire on the pile upon. We showed some of the photos and videos to retired US army lieutenant colonel James travellers who helped to train the Iraqi counter terror forces so you think this is Iraqis but of course absolutely. What do you say that having helped set up. This very I think it's horrible you don't behead someone and placed her head on the front of your humvee that's unacceptable because so war crime. It's of an atrocity it's it's it's it's demeaning it shows that they have no respect for human beings are human life it's barbaric that's why. This is a failure this is an absolute failure security policy for. US strategy against prices depends heavily on the Iraqi Army. Now being trained by American soldiers and provided with the one and a half billion dollars US weapons and equipment. Under American law credible evidence about gross violations of human rights by any security force of a foreign country. Requires the US to cut off date. It's called the Leahy law written by senator Patrick Leahy who examined ABC's photo file. The is going to be on indecency humanity are just total complete. Inexcusable. Atrocities. He says what he saw in those photos should trigger the law I would say that involves the Leahy law and and argue that we should be withholding money and it's a pretty clear cut case. The Iraqi Army says the photos and video could be ice is propaganda to naked soldiers looked back at the uniforms and patches can be bought in the market. But when we showed some of what we found two Iraqi Army spokesperson general -- Mon he promised a full investigation. As me as an Iraqi People have. The fight. This man who looked accent and about behavior lagged this. We'll look investigated these pictures will Mecca what decision about it. In Washington today the chairman of the joint chiefs general Martin Dempsey told senators he was concerned about possible war crimes when the militias taking the fight to slices along with the Iraqi Army. What we're watching carefully as weather and the the militias they call themselves the popular mobilization forces whether. When they recapture lost territory whether they engage in acts of retribution and and a ethnic cleansing. But what Dempsey did not say is that the US is also closely watching the Iraqi Army for war crimes in fact in a statement to ABC news the Pentagon says in the last six months it already has withheld assistance from certain Iraqi units on the basis of credible information in the fast. The barbarity of crisis has been condemned around the world. And there is little sympathy about what happens to them on the battlefield. From the images that were seen. It's very hard for an Iraqi civilian to tell who was the good guy and who's. Human rights activist along with the US government officials say. If Iraqi forces and militias are seen as behaving no differently than ices the effort against the terror group is doomed to fill. It's bad strategy for Iraq to think it could win a war and win the peace. With these kinds of atrocities. And it's folly for the US government to think that it will regains stability and security in Iraq. When the forces fighting in alliance with the US are carrying out these unbelievable atrocities. Brian Ross ABC news New York.
This transcript has been automatically generated and may not be 100% accurate.