At least 20 people were killed and 28 wounded in bomb attacks in Christian areas of Baghdad on Wednesday, police said.   A bomb in a parked car went off on Wednesday while worshippers were leaving a church in the Doura district of southern Baghdad after finishing prayers, police sources added. Two bombs also went off in a crowded market in a separate, mostly Christian area in Doura, killing six people and wounding 14, police and medics said. No one immediately claimed responsibility for the attacks.