One prisoner said two American soldiers had sex in front of him in the complex's hospital wing and another said he saw wires attached to the tongue and genitals of a cousin who was also being held.
The former inmates were part of a batch of some 315 prisoners scheduled to be freed from the jail at the centre of the prisoner abuse scandal, a day after a visit by US Defence Secretary Donald Rumsfeld.
The first busload left the complex, west of Baghdad, at
9:20 am (05:20 GMT), without stopping and passed about 100 people waiting outside, according to reporters.
The bus, flanked by US jeeps, arrived 30 minutes later at a base of the US-trained paramilitary Iraqi Civil Defence Corps (ICDC) at al-Amiriya on the western outskirts of Baghdad, where some of the detainees were set free. Other busloads were taken elsewhere in the country.
Speaking to reporters after he got off of the bus at al-Amiriya, Abu Mustafa, 24, said he was arrested 10 months ago by US forces who accused him of being a leader of a "terrorist" group.
"They kept me in solitary confinement for six days," he said.
"They hung me by my hands from the wall for five hours."
"One day when I was in the hospital, a soldier came in and asked if I was a Muslim and then started having sex with another (female) soldier right in front of me."
Muhammad Zadian, 45, who said he was detained for four months, said he was also hung from a wall by his hands for hours while he was "asked to confess that I attacked the American forces".
One prisoner spoke of electric
wires being attached to the body
He added: "I saw them attach electric wires to the tongue and the genitals of my cousin. They also used to give me a box of food and made me carry it around for six hours without putting it down."
Muhammad Khazal Al-Mussawi, 31, who was held for eight months, said he went into the prison weighing 117 kilos, and came out more than 30 kilos lighter.
"One of the soldiers told the prisoners that if it was in his hands, he would kill all the Iraqis," he said.
The allegations could not be independently verified.
Brigadier General Mark Kimmitt, deputy director of US military operations, announced on Wednesday that 315 prisoners would be released on Friday, with another release set for a week later.
"They kept me in solitary confinement for six days ... They hung me by my hands from the wall for five hours"
Abu Mustafa, 24
The US-led occupation has embarked on a prisoner release policy to try to reduce numbers by half to fewer than 2000, according to officials.
Photographs showing violent and sexual abuse of detainees at Abu Ghraib have shocked the world and prompted calls for US Defence Secretary Donald Rumsfeld to take responsibility by resigning.
Abu Ghraib, some 32km west of Baghdad, was where thousands of political prisoners were tortured and executed under former dictator Saddam Hussein.
Despite the huge death toll from Saddam's time and a US investigation that has seen seven US soldiers charged with criminal offences few of those outside the jail were convinced that much had changed. Courts martial have already been announced for three of the seven.