US military officials say four American soldiers have been charged with assaulting Iraqi prisoners of war - the first such charges to be brought.
Amnesty has criticised conditions for Iraqi POWs
The four face charges of punching, kicking and breaking the bones of POWs at the largest detention centre in Iraq, Camp Bucca near Umm Qasr.
All deny the charges and say the injuries were inflicted during self-defence when they were attacked by POWs.
The soldiers are confined to base in Kuwait while military prosecutors decide whether to proceed with courts martial.
Last month Amnesty International complained about the treatment of Iraqis in US custody.
It warned that the "conditions of detention Iraqis are held under... may amount to cruel, inhuman or degrading treatment or punishment, banned by international law".
The organisation said hundreds of people have been held without shelter or basic sanitation and denied access to lawyers.
The charges were denied by the Pentagon.
The human rights campaigners urged the US to give detainees access to family and lawyers and to investigate reports of mistreatment of prisoners, including death in custody.