Democratic Senator Jeff Bingaman of New Mexico expressed "deep concern" over the treatment of detainees in Iraq, Afghanistan and the US naval base at Guantanamo Bay, Cuba.

"Recent reports indicate that not only were detainees mishandled and interrogated in a manner inconsistent with the Geneva Conventions, but that subsequent internal reports of abuse appear to have been suppressed," he wrote to Rumsfeld in the letter released by the American Civil Liberties Union (ACLU).

Bingaman cited a Defense Intelligence Agency memo, obtained by the ACLU and released this week, accusing members of a special operations task force in Iraq of punching a prisoner in the face and then confiscating photos of the injuries taken by a DIA interrogator.

"While the abuse of detainees is unacceptable under any circumstance, reports of the suppression of evidence regarding abuse are extremely disturbing," he wrote in the letter dated December 9.

"It is for this reason that I urge you to expeditiously investigate the allegations of suppression and take immediate action to make public all documents related to cases of detainee abuse not critical to national security," he wrote.

The ACLU commended the senator's letter.

"What is most disconcerting is that this is probably only the tip of the iceberg," ACLU legislative office director Laura Murphy said in a statement.

"Sadly, the government has tried to hide these abuses behind a could of secrecy," she said. "That cloud must be lifted so that the country can get to the bottom of this."

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