BAGHDAD, Iraq - Fistfights broke out Friday around Najaf's most sacred shrine, a day after U.S. troops refused to intervene when gunmen loyal to a radical cleric ransacked an Iraqi police station there. Coalition forces came under fire in another Shiite city south of Baghdad. In the capital, a car bomb exploded on a highway in the Sayediya district as a U.S. patrol passed nearby. Two U.S. Humvees were slightly damaged but there was no U.S. confirmation of any casualties. The trouble in Najaf started Friday morning when hundreds of protesters marched toward the Imam Ali Shrine to express support...