WASHINGTON, May 5: Several major human rights groups on Wednesday demanded a congressional investigation into torture of prisoners by American soldiers in Iraq. Some also called for international inspections of all American detention facilities in Iraq, Afghanistan and Guantanamo Bay.

Human Rights Watch, a New York-based leading human rights group, demanded a broad public investigation of all detention centres around the world run by the US military and CIA.

The CIA operates an unknown number of small prisons for suspected terrorists overseas. In a letter to US National Security Adviser Condoleezza Rice, the group said: "The brazenness with which the US soldiers involved conducted themselves suggests they thought they had nothing to hide from their superiors."

A probe of conditions at Baghdad's Abu Ghraib prison "does not nearly go far enough to reverse the extraordinary harm these abuses have caused," the letter said. "There is a real crisis of leadership in Iraq - with double standards and doublespeak on human rights," Amnesty International observed.

The Amnesty demanded a fully independent, impartial and public investigation into all allegations of torture, adding that nothing less would suffice.