The gunmen showed up in four-wheel drive vehicles before storming the buildings in the Zayounah neighbourhood in eastern Baghdad, officials said. They added that at least 18 people were wounded.
Police have cordoned off the area.
The Interior Ministry and hospital officials confirmed the casualty figures.
The motive behind the killings was not immediately clear.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? firstname.lastname@example.org