BAGHDAD | Iraqi security forces, after more than of 40 days of intense fighting, on Thursday told residents to evacuate their homes in the Baghdad Shiite Muslim slum of Sadr City.</p><p>They were told to move to temporary shelters on two soccer fields.</p><p>The military&#8217;s call indicated the possibility of stepped-up military operations. It came as Iraqi security forces raided the radio station run by backers of Shiite cleric Muqtada al-Sadr, and militants launched rockets at a coalition force operating base in Basra. The attack killed two contractors and injured four civilians and four coalition soldiers.</p><p>Sadr City has been a battleground since late March, enduring fighting between U.S. and Iraqi forces and the militia loyal to al-Sadr.</p><p>Already about 8,500 people have been displaced from the slum of some 2.5 million people, according to the Iraqi Red Crescent. For weeks, food, water and medical shortages have affected about 150,000 people, aid agencies said.</p><p>The soccer fields are expected to receive some 16,000 evacuees.</p><p>The U.S. military is putting up barriers to isolate the southern portion of the city, about 2 square miles, where they believe militants are launching rockets into the heavily fortified Green Zone, home to Iraqi government offices and the U.S. diplomatic mission. The walls will isolate about 800,000 people in the slum from the rest of the district to stem the flow of rockets and weapons, said Col. Allen Batschelet, the chief of staff of the U.S. military Baghdad command.