Evidence of more prisoner abuse in Iraq has come to light after the US military was forced to release it by the courts.
The cases follow the Abu Ghraib prison scandal
The documents show that US marines carried out a mock execution, used electric shocks and burned prisoners.
American campaign groups obtained the US navy documents by using freedom of information legislation.
The navy said those found guilty of abuse had been punished, but added that many allegations - some relating to killings - had been dismissed.
incidents of detainee abuse were detailed, leading to the court martial conviction of 13 marines, and the jailing of some others.
All the names in the documents have been blacked out.
The cases follow the Abu Ghraib scandal, in which photos showed US guards at an Iraqi prison physically and sexually abusing inmates.
On Monday the Pentagon was forced to admit it was investigating more deaths in custody in Afghanistan that it had previously acknowledged.
The reports on abuse in Iraq released on Tuesday were drawn up by the Naval Criminal Investigative Service.
In one of the documents, a navy investigator describes his caseload "exploding" with a welter of "high visibility cases".
Ordered to kneel
"This kind of widespread abuse could not have taken place without a leadership failure of the highest order," said Anthony D Romero, director of the American Civil Liberties Union, one of the groups given access to the documents.
In one of the incidents, a witness described a marine
"shock an Iraqi detainee with an electric transformer".
Two US servicemen were jailed over the incident, the files reveal.
Three marines were convicted after they "ordered four juvenile Iraqi looters to kneel beside two shallow fighting holes and a pistol was discharged to conduct a mock execution".
The Pentagon said many accusations had been checked and found to be unsubstantiated.
"The fact that these cases have been investigated
underscores the point that we've been making, which is when we have credible allegations of abuse we take them seriously and investigate them," said a spokesman.