A parked car bomb exploded in a largely Shiite neighborhood of central Baghdad on Wednesday as the US defense secretary visited the Iraqi capital to assess whether the downturn in violence in parts of Iraq country can be sustained. Casualties were reported, police said, and gunfire and explosions followed shortly after the blast in the Karradah neighborhood. It was at least the fourth car bomb in Iraq on Wednesday. Earlier, a blast went off in the northern city of Mosul. Police said explosives hidden in a parked car killed a civilian and wounded seven others across the city from the US military base where Gates arrived. The deadliest attack Wednesday was in Baqouba, 60 kilometers northeast of Baghdad, where a suicide car bomber targeted a bus station and killed five civilians, police said. At least 20 others were wounded.