National Security Adviser Condoleezza Rice today issued a public apology to the Arab world for abuse of Iraqi detainees at Abu Ghraib prison.

In an interview with the al Arabiya television network, a regional network broadcast from the United Arab Emirates, Rice expressed sorrow about the treatment of the Iraqi detainees and said the United States regrets the humiliation caused to Iraqi detainees and their families.

"The American president is reacting because no American wants to be associated with any dehumanizations now of the Iraqi people. We are deeply sorry for what has happened to these people and what the families must be feeling. It's just not right. And we will get to the bottom of what happened," Rice said.

"It's simply unacceptable that anyone would engage in the abuse of Iraqi prisoners," she said.

Also today, Secretary of State Colin L. Powell said that the photos had "stunned every American. It was shocking. It showed acts that are despicable," he told reporters after a meeting with Secretary General Kofi Annan at the United Nations headquarters in New York.

As the probe of the alleged abuse continued, the Army today disclosed that it is investigating 10 prisoner deaths in Iraq and Afghanistan and 10 alleged assaults on prisoners since December 2002, the Associated Press reported. Maj. Gen. Donald Ryder, the Army's provost marshal, said investigators also looked at 12 other deaths in the prisons and found that they were the result of natural or unidentifiable causes.

In one other case, a U.S. soldier was found guilty in the death of a prisoner and was discharged from the service, military officials told AP.

At a Pentagon news briefing, Defense Secretary Donald H. Rumsfeld called the reports of prisoner abuse "deeply disturbing," but he defended the military's investigation of the incidents and promised to "hold accountable those who may have violated the code of military conduct and betrayed the trust placed in them by the American people."

Rumsfeld said he had asked for an investigation of other military detention facilities, such as the one at Guantanamo Bay, Cuba, and the Charleston Naval Station Brig. In response to a question about whether officials have indications of problems elsewhere, he said, "there are always allegations and charges of abuse in detention facilities," and added that it would be "premature for me to try to" answer that question today.

He spoke shortly after key members of the Senate, who were briefed by military officials today, complained to reporters about the Defense Department's handling of the allegations, saying they would summon officials to explain what happened and why Congress was not informed of it sooner.

Sen. John W. Warner (R-Va.), chairman of the Senate Armed Services Committee, called the situation "as serious a problem of breakdown in discipline as I've ever observed" in the armed forces.

Sen. John McCain (R-Ariz.) said it was "really egregious" for the Pentagon to have let the story come out in the news media before describing the problem to congressional oversight committees. "It's a neglect of the responsibilities that Secretary Rumsfeld and the civilian leaders of the Pentagon have to keep the Congress informed of an issue of this magnitude," said McCain.

For his part, Rumsfeld listed the various military investigations of the alleged prison abuse and argued that the public was apprised of the incidents, including a brief news release issued by U.S. Central Command on Jan. 16 announcing the investigation and comments to reporters that day by Army Brig. Gen. Mark Kimmitt, the military's deputy director of operations in Baghdad. Rumsfeld said that although it takes time, the investigations must be handled properly so that justice can be served.

"I recognize the appetite of people for instant information and instant conclusions," Rumsfeld said. "These things are complicated. They take some time. . . . And they're proceeding -- everything I can see -- in a very systematic, appropriate way."

When asked specifically about the criticisms leveled by senators today, the defense secretary said, "Well, we informed the world on January 16th that these investigations were underway. It seems to me that that is a perfectly proper thing to do. The investigations were announced. The world knew it."

Rumsfeld told reporters that he dismisses comparisons between the alleged abuse by the U.S. military and the abuses of former Iraqi leader Saddam Hussein.

The current controversy "is an exception," he said. "The pattern and practice of the Saddam Hussein regime was . . . to murder and torture, and the killing fields are filled with mass graves. And equating the two, I think, is a fundamental misunderstanding of what took place."

In contrast to Rice, Rumsfeld refused to apologize for the alleged abuses when asked by a reporter if such a remark would help ease complaints by Iraqi citizens about U.S. behavior.

"We have to deal with this issue from a standpoint of the Uniform Code of Military Justice. We have to deal with it from the standpoint of how we're organized and trained and led. And that has been my focus," Rumsfeld said. "There may be things that we can do that would be helpful in helping the world understand that this is an exceptional situation. It is not a pattern or a practice, and any suggestion that it is, I think, would be incorrect."

The senators' comments followed a briefing for the Armed Services Committee by Army Gen. George Casey, Army vice-chief of staff, which members said left them still in the dark as to the extent and severity of the abuse and the adequacy of the military's response to it.

Warner chastised the Pentagon for not being "forthcoming," saying it should have "informed the Congress of this earlier on, perhaps as early as the first knowledge came to the department. . . . "

"We will hold that hearing, a public hearing, at the first opportunity we can . . . ."

"The actions of these individuals have jeopardized members of the armed services in the conduct of their mission and have jeopardized the security of this country," said the committee's ranking Democrat, Sen. Carl M. Levin (Mich.) "It's a few individuals that have apparently conducted these despicable actions. We hope it's a few. We don't know how systemic it is."

It particularly troubled committee members that they heard about the severity of the allegations on CBS's "60 Minutes," which first displayed photos of the abuse of Iraqi prisoners that have now been broadcast across the globe.

"It is a severe problem," said McCain. "It is a pattern on the part of the Defense Department of not keeping the Congress informed on a variety of issues. But this is really egregious."

"The dissatisfaction in the committee is that we were not informed as to the investigation nor the results of the investigation," said McCain. "And the way that we were informed, of course, was through media reports. The Congress should have been notified of this situation a long time ago.

Other senators, in other forums, said they were shocked by a statement earlier this week from Air Force Gen. Richard B. Meyers, chairman of the Joint Chiefs of Staff, saying that he had yet to read the official report on prisoner abuse in Iraq.

"It was totally unacceptable for the head of the Joint Chiefs of Staff to be saying, on the second of May, that a report that came out on this subject in February was working its way up through the chain of command and he hadn't gotten it yet, but at some point in the future he expected to," said Sen. Jeff Bingaman, (D-N.M.) speaking on NBC's "Today" show.

"I think Senator Bingaman has it just about right," said Republican Sen. Chuck Hagel (Neb.), a decorated Vietnam veteran, also speaking on "Today."

"Obviously we must allow the military to conclude its investigations. And my understanding is that those investigations are going forward on many tracks. They need to be done very quickly. But there's no question the American people need to understand this . . .

"Was there an environment, a culture, that not only condoned this but encouraged this kind of behavior?

"Yes, we need to look well beyond just the soldier," said Hagel. "Who was in charge? Was there a breakdown in command here? There's no question we have a chain-of-command breakdown, and we need to understand all the dynamics of this. So the Congress is going to have to take a very hard look at this."

Sen. Edward M. Kennedy (D-Mass.) said after Casey's briefing that "the important point that I took from this hearing is that this does not appear to be an isolated incident and that there are additional reports in Iraq, and also Afghanistan. And I think we also have to find out if there -- the conduct of personnel down in Guantanamo as well. I think it's important we get the full range of this kind of despicable activity, not only in terms of the American military personnel, but also civilian contractors."

Staff writer Lexie Verdon contributed to this story.