BAGHDAD, Iraq — Two car bombs exploded in an outdoor market in Baghdad on Sunday, killing at least 56 people and injuring scores in the deadliest attack since U.S. and Iraqi forces began a major security push around the capital last week. The twin blasts tore through the open-air market in the mostly Shiite district of New Baghdad. The death toll was reported by police and ambulance service officials on condition of anonymity because they were not authorized to speak to media. At least 127 people were injured, said a police official.