Defense Secretary Donald Rumsfeld on Friday offered his "deepest apology" to Iraqi prisoners abused by US troops as he appeared before a congressional committee hearing marked by a noisy protest.

Rumsfeld, fighting for his job according to US media, said the United States had an obligation to treat prisoners correctly.

"We didn't, and that was wrong," he said. "So to those Iraqis who were mistreated by members of the US armed forces, I offer my deepest apology."

Rumsfeld told lawmakers: "It happened on my watch, and I take full responsibility."

Minutes after the start of the committee hearing, during Rumsfeld's statement, protesters disrupted the hearing and shouted demands for Rumsfeld to be sacked.

About eight demonstrators shouted "fire Rumsfeld" and held up paper placards, halting the defense secretary's testimony before the Senate Armed Services Committee hearing.

Security guards escorted the protestors out of the chamber.

The defense secretary and General Richard Myers, chairman of the US joint chiefs of staff, appeared before the committee along with other top military brass amid an international outcry over pictures of bound and naked prisoners being abused at the US-run Abu Ghraib prison near Baghdad.

Rumsfeld has already been scolded by President George W. Bush for not telling him sooner about the photographs, which first came to light in January but were only publicised last week by the CBS television channel.

US lawmakers have expressed anger that they were not told about the investigation into the abuse.

Rumsfeld acknowledged his failure to disclose details.

"Let me be clear, I failed to recognize how important it was to elevate a matter of such gravity to the highest levels, including to the president and members of Congress," Rumsfeld told lawmakers. HUMAN RIGHTS WATCH DEMANDS ACCESS TO US ARMY DETENTION FACILITIES

Meanwhile, in a letter to Rumsfeld, Friday, Human Rights Watch arged that the US government should allow human rights groups to monitor detention facilities in Iraq and elsewhere in order to halt the abuse of prisoners. “Torture flourishes in the dark,” said Kenneth Roth, executive director of the New York-based rights monitor. “If the Bush administration really wants to put a stop to torture in US detention facilities, it has to open them up to outside scrutiny.”

Rumsfeld was scheduled to testify before Congress on Friday, a day after President George W. Bush was forced for the first time to apologize for the abuse of Iraqi prisoners by the US-led occupation force.

To lend credibility to any inquiry into the scandal, Human Rights Watch said the government needed to permit independent, impartial and public investigations of all facilities where the US military and intelligence community are holding detainees.

”The United States has lost the ability to ensure that its own investigations will be considered impartial and independent,” Roth said. “Independent monitoring organizations report their findings publicly, and that’s very important in this climate.”

Human Rights Watch also called on Rumsfeld to ban all “stress and duress” interrogation techniques, including extended sleep and sensory deprivation, forced standing and binding detainees in painful positions.AFP