The clash occurred after another soldier was killed in an insurgent attack on an army patrol. Police sources said a civilian was shot dead as troops opened fire to clear the way for their convoy taking wounded soldiers to the hospital.
Police said the fighting between the army units broke out as one patrol tried to remove its wounded soldiers from the hospital, and a second unit tried to stop them.
The U.S. military is training Iraqi forces to take over security operations to pave the way for U.S. troop withdrawals.
In separate incidents today, a U.S. soldier was killed when a roadside bomb hit his vehicle south of Baghdad. And a police officer was killed in an explosion at his home near Hillah.
(compiled from agency reports)