The benchmark Korea Composite Stock Price Index was up 13.36 points, or 0.56 percent, to 2,379.76 as of 11:20 a.m.
Institutions and foreigners bought a combined 140 billion won ($124 million), offsetting net selling worth 156 billion won by individuals.
A tight range is widely expected this week ahead of the US Federal Reserve's annual economic policy symposium in Jackson Hole, Wyoming.
Large-cap stocks traded mixed across the board, with market bellwether Samsung Electronics Co. falling 0.04 percent and No. 2 chipmaker SK hynix Inc. rising 0.59 percent.
Top carmaker Hyundai Motor Co. fell 0.34 percent, and leading cosmetics company AmorePacific Corp. climbed 5.53 percent.
The local currency was trading at 1,128.55 won against the US dollar, up 3.25 won from the previous session's close. (Yonhap)