The website Wikileaks has released almost 400,000 secret American military records, which suggest US commanders ignored evidence of torture by the Iraqi authorities.
The documents also suggest hundreds of civilians were killed at US military checkpoints after the invasion in 2003.
The files show the US kept records of civilian deaths, despite previously denying they had.
The death toll was put at 109,000 of whom 66,081 were civilians.
The BBC reports that one detainee with extensive acid burns said that he'd had chemicals poured on his hands and had his fingers cut off.
The documents also show that on many occasions the US military made initial reports but under orders did not pursue investigations.
Another incident documented appears to reveal a US Apache helicopter being cleared to fire on a group of Iraqi insurgents, who seemed to be attempting to surrender, because the crew was told they could not surrender to aircraft and therefore were valid targets.
American Secretary of State, Hillary Clinton, said she condemned "in the most clear terms the disclosure of any information by individuals and or organisations which puts the lives of United States and its partners' service members and civilians at risk".
Wikileaks previously published more than 70,000 secret papers about the war in Afghanistan in July.