As fighting continued between Iraqi security forces and Shiite militia fighters in the oil-rich port city of Basra, Prime Minister Nouri al-Maliki gave an ultimatum Wednesday for gunmen to lay down their arms and forsake violence by week's end.

Iraqi police and soldiers battled Muqtada al-Sadr's Mahdi fighters Tuesday for control of key neighborhoods in Basra, the country's second-largest city, as the radical Shiite cleric threatened a countrywide campaign of civil revolt.