keywords: najaf clashed militiamen shi militia
text: U.S. Troops Clash with Shi'ite Militia in Najaf  NAJAF (Reuters) - U.S. troops clashed with Shi'ite  militiamen in Najaf on Saturday, interrupting a day of relative  calm in the holy city with the sound of mortar,  rocket-propelled grenade and machinegun fire, witnesses said.