Iraq is investigating allegations of abuse after more than 160 prisoners were found locked in an Interior Ministry bunker in Baghdad, many of them beaten and malnourished and some apparently tortured.
The detainees were discovered on Sunday night during a raid by US troops who were searching for a missing teenage boy.
The prisoners were found in an underground cell near an Interior Ministry compound in Jadriya, a central Baghdad neighbourhood, and many of them showed signs of malnourishment and beatings, Iraqi officials and US military sources said.
"There were 161 detainees in all and they were being treated in an inappropriate way ... they were being abused," Hussein Kamal, a deputy interior minister, told Reuters.
"I've never seen such a situation like this during the past two years in Baghdad, this is the worst," he told CNN.
"I saw signs of physical abuse by brutal beating, one or two detainees were paralysed and some had their skin peeled off various parts of their bodies."
"This is totally unacceptable treatment and it is denounced by the minister and everyone in Iraq," he told Reuters.
Kamal said the detainees had all originally been detained with arrest warrants. They had now been moved to another facility where they were receiving medical assistance.
It was not clear why they had been arrested in the first place. Most detainees are suspected of supporting the Sunni Arab insurgency against the Shi'ite- and Kurdish-led government.
Iraq's Sunni Arab minority has accused militias linked to the Shia-run Interior Ministry and Shia political parties of rounding up Sunnis in raids and holding them without charge. The government has denied the accusations.
Kamal said Prime Minister Ibrahim Jaafari, a Shi'ite, had ordered an investigation into the case of the prisoners in the bunker, to be led by the deputy prime minister, a Kurd.
US military sources said troops were shocked when they came across the prisoners, some of whom showed the marks of beatings and looked like they had not been fed well for weeks.