South Korean stocks opened nearly flat Wednesday as investors remained cautious ahead of the Federal Reserve's September policy decision and amid rising oil prices and Middle East tensions. The benchmark Korea Composite Stock Price Index gained 0.69 point, or 0.01 percent, to 6,627.95 as of 9:15 a.m. Brent crude futures rose more than 2 percent to above $108 a barrel after a Saudi oil pipeline was attacked and Yemen's Houthi rebels seized more islands along Red Sea shipping routes. The S&P 500 fell 0.45 percent and the Nasdaq dropped 0.78 percent overnight, while the 10-year U.S. Treasury yield rose above 5 percent for the first time since July 2007. Samsung Electronics was flat, while SK hynix, LG Energy Solution and Hanwha Aerospace gained; Hyundai Motor fell. The won strengthened 1.2 won to 1,365.8 per dollar.