The allegations extend beyond recent reports of at least 173 prisoners found malnourished and possibly tortured by Iraqi security forces in a Baghdad lockup, Manfred Nowak, the United Nations' special investigator on torture, said on Wednesday.
Nowak said he was "not surprised" by Prime Minister Ibrahim al-Jaafari's disclosure on Tuesday of the mistreatment of the Iraqi Interior Ministry prisoners because he has received "various allegations" of torture and degrading treatment by both US and Iraqi forces in Iraq.
"That torture is still practised in Iraq after Saddam Hussein, that is no secret," he told The Associated Press in a telephone interview from Vienna, Austria.
"It is shocking, but on the other hand, we have received allegations of these secret places in Iraq already for quite a long time," Nowak said.
He said it was difficult to say how many such places might exist in Iraq because former prisoners were often hooded, blindfolded or disoriented while being transported and detained.
Torture allegations involve both
Iraqi and US detention centres
Concerning a separate allegation that US forces used caged lions in a Baghdad palace in 2003 as part of a terrifying interrogation, Nowak said: "I have not heard that before. ... It is a new allegation."
US Army spokesman Paul Boyce said Tuesday there is no formal investigation of the allegations made by former prisoners Mohammed Sabbar and Sherzad Kamal Khalid.
Boyce said the use of lions never came up in any of the more than 400 investigations into detainee abuse conducted by the military over the past three years.
US Defence Department officials suggested that at times detainees make up claims of abuse.
Nowak said: "It only means that there is need for an impartial and independent investigation."
He added that the other claims by Sabbar and Khalid - including alleged sexual abuse, mock executions, electric shock and water and food deprivation - were consistent with other allegations he has received from former inmates at US detention centres.
"These are the usual type of allegations," he said.
UN investigators have been seeking access to US and Iraqi-run detention centres in Iraq since June 2004, but have yet to receive a response from either government, Nowak said.
"As long as there is no official reaction to any kind of UN request for a visit, very little can be done," he said.