It is also about 500m from a Sunni shrine.About an hour earlier, a suicide car bomber crashed into an Iraqi police checkpoint at an entrance to Sadr City, the capital's biggest Shiite Muslim neighborhood and a stronghold for the militia led by radical anti-US cleric Moqtada al-Sadr.The explosion killed at least 30 people, including five security officers, and wounded 45, police said.Black smoke bi