The questioning of hundreds of  Iraqi prisoners last fall in the newly established  interrogation centre at Abu Ghraib prison yielded very little  valuable intelligence, a media report said on Thursday quoting civilian and military officials.

The interrogation centre was set up in September to obtain better information about insurgency in Iraq, which was better organised and more vigorous than the US had expected, prompting concern among generals and Pentagon officials who were unhappy with the flow of intelligence to combat units and to higher headquarters, it said.

But civilian and military intelligence officials, as well as top commanders with access to intelligence reports, told the New York Times that they learned little about the insurgency from questioning inmates at the prison.

Most of the prisoners held in the special cellblock that became the setting for the worst abuses at Abu Ghraib apparently were not linked to the insurgency, they said.

All the prisoners sent to Abu Ghraib had already been questioned by the troops who captured them for urgent information about roadside bombs, imminent attacks and the like.

The officials, the paper said, could not say whether the harsh interrogation methods used at Abu Ghraib were counterproductive.

The officials, however, said few if any prisoners there had been able to shed light on questions to which General John P Abizaid, the top American commander for the Middle East, and his deputies had assigned highest priority, including the whereabouts of Saddam Hussein and the nature of the insurgency's leadership.

"Most of our useful intelligence came from battlefield interrogations, and at the battalion, brigade and
division-level interrogation facilities," a senior military intelligence officer who served in Iraq told the Times.

Once prisoners were sent on to Abu Ghraib, the officer said, "We got very little feedback."

The paper quoted one American general, who recently returned from Iraq, putting the concerns of many senior
officers about what happened to the detainees this way: "There was a sense when someone was sent down there, they went into a black hole and never came out."

In Senate testimony last week, General Abizaid defended interrogation practices used in Iraq, saying the
information obtained served to save American lives.

But he made no specific mention of Abu Ghraib, and military officers told the paper that the kind of intelligence he was referring to, about the location of hidden explosives or the details of planned attacks, had been obtained more often by soldiers in the field.

General Abizaid made clear in his testimony that the intelligence-gathering effort that he and Lt Gen Ricardo S Sanchez, the top American commander in Baghdad, set in motion late last summer had fallen short of its intended goal of getting a clear picture of the insurgency.