Hundreds of South African soccer fans disgruntled at the performance of their team rioted at a game on Saturday night. They assaulted at least one security guard on the field, attacked others with chairs, set parts of the stadium on fire and caused extensive damage. They were shocking scenes in a country that has hosted the World Cup and prides itself on having the best-run soccer league in Africa. Police said Sunday that two people had been arrested and more arrests were imminent following the mayhem at the Moses Mabhida Stadium in the east coast city of Durban.