Two provincial banking firms won the bid Tuesday to each buy a regional bank unit of Woori Finance Holdings Co., giving a hand to the government's long-pending sale of South Korea's largest banking group, bank and regulatory sources said. The state-run Korea Deposit Insurance Corp. (KDIC), the controlling shareholder of Woori Finance, picked Busan-based BS Financial Group Inc. as the preferred bidder for Kyongnam Bank, and JB Financial Group Co., based in the southern city of Gwangju, for Kwangju Bank.