Residents say Iraqi soldiers are warning people to leave their homes in Sadr City for security reasons.
They say the warning is the first time residents have been told to flee the embattled Baghdad district. The residents say soldiers using loudspeakers are telling people to go to nearby soccer stadiums. But most residents still have not left.
Thursday's warning is taken as a sign that U.S.-backed forces are preparing to launch a new push into the area to clear pockets of Shiite extremists who have been battling U.S. soldiers for almost seven weeks.
A U.N. agency says about 6,000 people have fled their homes in the Shiite militia stronghold.