Korea Gas Corp. on Tuesday reported its fourth-quarter net loss of 657.3 billion won (US$493.8 million), swinging from a profit of 887.7 billion won a year earlier.The company said in a regulatory filing that operating income for the October-December period fell 52.6 percent on-year to 529.6 billion won. Sales decreased 41.6 percent to 10.6 trillion won.Source: Yonhap News Agency