BUKAVU, Congo — Rwanda-backed rebels have "occupied" a second major city in mineral-rich eastern Congo, Congo's government said Sunday, as M23 rebels positioned themselves at the governor's office in Bukavu and pledged to clean up after the "old regime." Associated Press journalists witnessed scores of residents cheering on the rebels after they entered Bukavu following a dayslong march from Goma, a city of 2 million people they seized last month. The rebels saw little resistance from government forces against the unprecedented expansion of their reach after their years of fighting. Congo's government vowed to restore order in Bukavu, a city...