US President George W Bush has reacted with "disgust and disbelief" to more images of alleged prisoner abuse by US guards in Iraq, his spokesman said.
New evidence of alleged prisoner abuse is coming to light
Mr Bush viewed the classified images at a meeting with advisers and defence staff at the Pentagon, which is mulling whether to release them to the media.
They included images of a sexual nature, a Pentagon spokesman added.
The statement came as the general who wrote a report on prisoner mistreatment prepares to testify before Congress.
In his findings, which were delivered to the Pentagon in February, General Antonio Taguba said guards at Baghdad's Abu Ghraib prison committed "sadistic, blatant, and wanton criminal abuses".
General Taguba's testimony to the Senate Armed Services Committee - due on Tuesday - could well throw new light on the extent to which the abuse was directed by senior officers, the BBC's Justin Webb reports from Washington.
Our correspondent adds that the prison scandal appears to be having a severe effect on the American public's view of the entire Iraq war.
The latest nationwide opinion poll suggests, for the first time, that a majority now believe it was not worth fighting.
Meanwhile a Red Cross report - which has been leaked to the press - suggests that up to nine out of 10 coalition detainees in Iraq are arrested by mistake.
Citing coalition intelligence officers, the 24-page report passed to the coalition by the International Committee of the Red Cross in February also found evidence of widespread and routine abuse of prisoners.
President Bush came to the Pentagon on Monday in a public show of solidarity with Defence Secretary Donald Rumsfeld, who has been widely condemned over the allegations of abuse.
Mr Bush described Mr Rumsfeld's work as "superb".
The president then went behind closed doors to view photographs and video clips which officials stressed had not been released to the media.
Larry Di Rita, Mr Rumsfeld's spokesman, said the "disturbing" images showed the humiliation of prisoners as well as "inappropriate behaviour of a sexual nature".
8,000 prisoners held in 14 separate jails
Three main prisons - Abu Ghraib and Camp Cropper in west Baghdad; Camp Bucca, near Umm Qasr - hold inmates for extended periods
Almost all inmates are "security internees" - suspected of posing a threat to the coalition
"The president's reaction was one of deep disgust and disbelief that anyone who wears our uniform would engage in such shameful and appalling acts," White House spokesman Scott McClellan said later.
No details of the images viewed at the Pentagon were given.
But the man who published the first snapshots of prisoners being abused in the New Yorker magazine, Seymour Hersh, has told the BBC's World Today programme that more are on the way.
He said that images he had seen appeared to have been taken by a different unit from that involved in the photos initially published.
"So the notion that was promulgated initially last week or the week before by the American authorities... that this is just a bunch of six or seven bad seeds, that's pretty much shot by these photos," he said.
The reporter said it was clear there was, or had been until recently, a "very systematic problem" in the prison systems in Iraq.