BAGHDAD, Iraq (AP) - Three U.S. Marines assigned to the Army's 1st Brigade, 1st Armored Division have been killed in action in Anbar province, the U.S. military said Saturday. The Marines died Thursday, according to a U.S. statement. No further details were released.Both Army and Marine units operate in the Ramadi area of Anbar, and individuals from both services are sometimes attached to units from the other.