Iran struck back at the United States for the killing of a top Iranian general early Wednesday, firing a series of ballistic missiles at two Iraqi bases housing U.S. troops in a major escalation that brought the two longtime foes closer to war.

Several mortar rounds on Saturday struck an Iraqi air base housing U.S. troops, hours after thousands of Iraqis packed the streets here to mourn two senior military commanders killed in a U.S. airstrike.