A bomb ripped through a crowded market in Baghdad's main Shiite district, killing at least 69 people and wounding more than 100 less than a week before a deadline for US combat troops to leave Iraq's urban areas. A series of blasts this week have killed more than 160 people, as US and Iraqi officials warned they expected more violence before the US withdrawal from cities. In the past, bombings in Shiite areas would be followed by mortar attacks against Sunni strongholds or execution-style killings that were the signature of Shiite militias. The bomb, which was hidden under vegetables on a motorized pushcart, exploded about 7 pm on Wednesday, apparently timed to maximize casualties by striking shoppers buying food for their evening meal at the Mradi market. Shrapnel was blown more than 600 yards away and some shops were set on fire, a police officer said. An Interior Ministry official said 69 people were killed and 135 wounded.