US troops killed five gunmen and detained three suspected Shi'ite militiamen in a raid in eastern Baghdad early on Monday, the US military said.
The raid targeted a commander of a special group who has ties to the current kidnapping network and is involved in directing the recent explosively formed penetrator, or EFPs, and improvised explosive device (IED) attacks in the area, the military said in a statement.
The Special Groups are militia extremists, said to have been funded, trained and armed by Iranian Revolutionary Guards Corps' - Quds Force - operatives.
The troops received small arms fire when they arrived at their targets and returned fire, killing four gunmen and wounding three others.
Another suspect was killed as he was planting a roadside bomb on the route of the US troops, it said.
The US military said the Special Groups have evolved over the past three years into what are largely rogue elements that use a cellular structure to operate independently.
The US forces frequently accuse Iran of arming and training Iraqi militias to stir up chaos in the war-torn country but Iran denies.