Bakhtyar Amin said he believed two US troops had opened fire on rioters but he did not know why. His ministry has sent a delegation to the camp in southern Iraq to investigate.

   

"If there is a mistake, then those in charge should be brought to account," Amin said on Tuesday.

   

"If we are convinced there was no justification for the degree of force used, then we want them to be tried," he added.

 

"That is what the American side says as well."

  

The riot broke out on Monday at Camp Bucca, near the Kuwaiti border, where more than 5000 inmates are housed at the US military's main prison camp in Iraq.

 

Rocks thrown

   

Prisoners began throwing rocks and fashioning weapons after a routine search of one of the camp's 10 compounds, the US military said. Violence then spread to three other compounds.

 

No Americans were injured in the
jail riot which lasted 45 minutes

Troops shot dead four men in the riot which involved hundreds of detainees, the US military said. Six people were injured, five of them by guards. Three of the wounded were taken to a military hospital where they were in a stable condition.

   

US commanders have said they want Camp Bucca to serve as a model for good conditions and as an antidote to the bad publicity generated by photographs of prisoner abuse last year at Abu Ghraib prison near Baghdad.

 

No Americans were seriously injured during the 45-minute riot, Lieutenant-Colonel Barry Johnson said.

 

Motive unknown

   

"We still have no clear motive for the disturbances and are awaiting a full report from the US army's criminal investigations division," Johnson, a spokesman for the US military detentions operation in Iraq, said.

   

The military said tension between Sunni and Shia Muslims has been simmering at Camp Bucca since Ramadan late last year, although this was not necessarily the cause of Monday's riot.

 

"If there is a mistake, then those in charge should be brought
to account"

Bakhtyar Amin,
Iraqi Human Rights Minister

This is not the first time US soldiers have fired on Iraqi prisoners. A riot at Baghdad's Abu Ghraib prison in November 2003 left three detainees dead.

      

Some detainees have been held for more than a year in Camp Bucca's razor wire compounds, their cases reviewed by US and Iraqi officials every three to four months.

   

Johnson said the troops on guard were from a recently arrived reserve unit, the 105th Military Police Battalion.

   

He said he did not know if the riot was related to Sunday's election. None of the thousands of detainees in Iraq was able to take part because no provision was made for absentee voting.