Newly released U.S. Navy documents portray a series of abuse cases stretching beyond Iraq's Abu Ghraib (search) prison where photos surfaced this year of U.S. troops forcing prisoners — often naked — to pose in humiliating positions.

The files released Tuesday document a crush of abuse allegations, most from the early months of the U.S. occupation of Iraq, including U.S. Marines forcing Iraqi juveniles to kneel while troops discharge a weapon in a mock execution and the use of an electric shock on a prisoner.

The approximately 10,000 files include investigation reports from the Naval Criminal Investigative Service (search) and witness interviews.

All names have been blacked out in the documents, which were released after a federal court ordered the government to comply with a Freedom of Information Act (search) petition filed by the American Civil Liberties Union (search), the Center for Constitutional Rights (search) and other organizations.

"This kind of widespread abuse could not have taken place without a leadership failure of the highest order," said ACLU Executive Director Anthony D. Romero.

The Pentagon says cases of abuse are taken seriously and investigated.

"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 Maj. Michael Shavers, a Pentagon spokesman.

Some of the documents include the alleged executions of Iraqis. The Navy found the allegations to be "unsubstantiated" and closed the investigation. It remains unclear whether any other military branches are investigating.

In one of the reports, a Marine said he and two others were ordered to kill three Iraqis.

"The executions allegedly took place in early April 2003 while the unit was temporarily based at an abandoned Iraqi pharmaceutical factory south of Baghdad," according to the NCIS document, dated June 26, 2003.

The Marine said he was threatened with death if he did not carry out the order. The bodies of the dead Iraqis were allegedly dumped in a hole, the document said.

After the incident was reported, the Marines were interviewed. One, who was interviewed and advised of his rights, retracted his previous statements, saying the executions never took place.

He said he "made up the story to tell his friends ... unlike his colleagues, he didn't have good stories to tell about his deployment to Iraq," the report said. It added that the Marine said he was drunk and made up the story while at a party.

The suspect, whose name along with others allegedly involved was blacked out, was given a polygraph test, "an evaluation of the examination indicated (he) was being truthful in his responses."

Troops have said many of them are trained in ways to trick polygraph examiners. It was unclear whether the Marine was disciplined for the alleged fabrication.

At least 19 prisoner deaths in Iraq and Afghanistan have been investigated by the military; eight were determined to be justified killings of an escaping or dangerously violent prisoner.

Several Marines have been charged in connection with the treatment of a member of Saddam Hussein's Baath Party who died of strangulation after a Marine grabbed him by the neck at a holding facility. Investigators ruled that the death was accidental, but other investigations are pending.

In another of the documents, a Navy corpsman is quoted as saying, "there was a lot of peer pressure to keep one's mouth shut."

In yet another, a Navy investigator describes his Iraq caseload as "exploding" with "high visibility cases."

One case occurred on April 13 in al-Mahmudiya, Iraq, where a witness — whose name has been blacked out — saw a Marine "shock an Iraqi detainee with an electric transformer," holding "wires against the shoulder area of the detainee (who) danced as he was shocked."

Five suspects were involved in the case, according to the documents. One of them was found guilty of assault, cruelty and maltreatment, among other charges, and was sentenced to a year in the brig. A second suspect was found guilty of cruelty and maltreatment, and was sentenced to eight months.

The cases of the three others in the case are pending, according to the documents.

In a case from June 2003, Marines in Adiwaniyah ordered "four juvenile Iraqi looters to kneel beside a shallow fighting hole and a pistol was discharged to conduct a mock execution."

It was unclear from the redacted documents whether anyone was disciplined.