The benchmark Korea Composite Stock Price Index climbed 1.70 points, or 0.07 percent, to 2,492.19 in the first 15 minutes of trading.
Foreigners and retail investors bought a combined 55 billion won ($49 million) worth of stocks, offsetting 53 billion won sold by institutions.
Companies such as Samsung Electronics Co. and Hyundai Motor Co. are scheduled to release their third-quarter earnings results in the coming days.
Large-cap stocks were mixed across the board, with market bellwether Samsung Electronics leading the gains.
The tech giant gained 0.26 percent, but No. 2 chipmaker SK hynix Inc. fell 1.47 percent.
POSCO, the country's leading steelmaker, advanced 1.37 percent, and leading chemical firm LG Chem Ltd. advanced 0.51 percent. But top carmaker Hyundai Motor shed 1.99 percent.
The local currency was trading at 1,130.30 won against the US dollar, down 2.90 won from the previous session's close. (Yonhap)