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BAGHDAD, Dec 10 (Reuters) - Seven inmates in an Iraqi Interior Ministry jail were killed in a mortar attack in central Baghdad on Monday, an Iraqi security official said.

Another 21 people were wounded in their cells said the official, who asked not to be identified. Between two and three mortar rounds hit the facility, he said.

The U.S. military said it had received reports of an indirect fire attack on the jail but few other details were immediately available.

The jail mainly houses suspected insurgents. The majority of the thousands of prisoners in Iraqi jails are Sunni Arabs accused of attacks on the U.S. military and Iraqi security forces.

The security source said those wounded were still regarded as suspects and were being treated at the jail.

A U.N. human rights report this year expressed the "utmost concern" about the use of torture and "other inhumane treatment" in detention centres run by Iraq's Interior Ministry and the Defence Ministry.

Iraq's Shi'ite-led government has acknowledged some cases of abuse of detainees but has said torture was not systematic. (Writing by Paul Tait, Editing by Dean Yates)

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