A video leaked online shows US soldiers shooting dead civilians in Iraq and then laughing at their bodies, a media report said on Tuesday.
The footage on website WikiLeaks shows US forces firing on a group of men, some of whom are unarmed, Daily Mail reported.
Reuters photographer Namir Noor-Eldeen, 22, and his driver Saeed Chmagh, 40 were among those believed to have been killed in the attack. Two children were also wounded.
A US military spokesman has confirmed that the footage was authentic.
The website, WikiLeaks, said it acquired encrypted video of the attack from military whistleblowers and had been able to view it after cracking the encryption code.
It said the video was shot from an Apache helicopter gun-site and it showed a gunbattle in the New Baghdad district of the city July 12, 2007.
The video shows an aerial view of a group of men moving about a square in a Baghdad neighbourhood.
"The gathering at the corner that is fired upon has about nine people in it," Julian Assange, a WikiLeaks spokesperson, was quoted as saying.
The gunsight tracks the two Reuters news staff as the flyers identify their cameras as weapons.
The lead helicopter, using the moniker Crazyhorse, opens fire and one of the crew shouts: "Ha ha ha. I hit 'em'."
Another responded a while later: "Oh yeah, look at those dead b*****ds."
One of the men on the ground, believed to be Chmagh, is seen wounded and attempting to crawl to safety.
One of the helicopter crew is heard wishing that the man reaches for a gun so he has a reason for opening fire, and says: "All you gotta do is pick up a weapon."
A little later a van comes and begins helping the wounded. The helicopter opens fire, though sitting behind the windscreen are two kids.