(Adds details) BAGHDAD, July 3 (Reuters) - A car bomb killed 10 people and wounded 20 near an outdoor market in a Shi'ite neighbourhood of Baghdad on Tuesday, Iraqi police said. They said a parked car exploded in the district of Shaab just before nightfall, when many residents were out shopping. U.S. forces have put high concrete walls around a number of Baghdad's markets to protect shoppers from suicide car bombers, who try to strike places where people gather in large numbers. The U.S. military blames Sunni Islamist al Qaeda for most big car bombings that target civilians.