Coup plot in Iraq?

See the post below the picture for context, but Richard Engel of NBC news is reporting that the Iraqi Deputy Prime Minister told Engel that he had "evidence uncovered that the Iraqi military had been planning to stage a coup," and this was the reason for the unprecedented total curfew. (Link - the video on the right of this page.)

This story is moving, so it may change, but it has big ramifications. There will have to purges which will likely fracture Iraq further. What group was behind this? Is it the Sunni leadership in the military trying again?

Supposedly this coup "never got past the planning stage," but if that's the case, why the complete lockdown? Are they expecting sympathy violence? Or is the "planning stage" comment saying it was planned for tomorrow? Too many questions right now.