The benchmark Korea Composite Stock Price Index rose 10.04 points, or 0.42 percent, to 2,383.18 in the first 25 minutes of trading.
Foreigners became net buyers after dumping more than 830 billion won ($725 million) worth of stocks in the past four sessions due mainly to rising tensions between North Korea and the United States over the former's nuclear and missile development programs.
US President Donald Trump said Tuesday he is "totally prepared" to use the military options against North Korea. His latest warning came in response to Pyongyang's threat a day earlier to shoot down approaching American bombers, even if they are in international air space.
Most large-cap stocks advanced across the board.
No. 2 chipmaker SK hynix Inc. rose 0.60 percent, top carmaker Hyundai Motor Co. climbed 1.02 percent and leading steelmaker POSCO was up 1.43 percent.
But market bellwether Samsung Electronics fell 0.08 percent and leading mobile service operator SK Telecom was down 0.39 percent, keeping the KOSPI index from rising further.
The local currency was trading at 1,145.50 won against the US dollar, up 3.60 won from the previous session's close. (Yonhap)