Horrifying video footage showing 15 people including two Reuters journalists being shot dead by a US Army Apache helicopter gunman, taken from the helicopter's gun camera, appalled the world when it was released on Wikileaks.

The crew were heard laughing at the "dead b-----ds" and saying "light 'em up!" and "keep shooting, keep shooting".

The US military has refused to discipline the helicopter's crew, saying that there were "insurgents and reporters in an area where US forces were about to be ambushed.