The benchmark Korea Composite Stock Price Index fell 4.67 points, or 0.20 percent, to 2,367.58 as of 11:20 a.m.
The main index continued to fall for the eighth consecutive session mainly on foreign selling. Foreigners dumped more than 1 trillion won ($876 million) worth of stocks in the past seven sessions due mainly to the North Korea risks.
Foreigners offloaded large-cap stocks in the face of persistent North Korea risks, seeking safe assets such as the dollar.
US President Donald Trump said Tuesday he is "totally prepared" to use 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 airspace.
Large-cap stocks were mixed across the board.
Market bellwether Samsung Electronics Co. fell 0.46 percent, top carmaker Hyundai Motor Co. shed 0.34 percent and leading refiner SK Innovation Co. was down 1.02 percent.
Among gainers, No. 1 steelmaker POSCO rose 0.48 percent and dominant cosmetics maker AmorePacific Corp. gained 3.91 percent.
The local currency was trading at 1,146.15 won against the US dollar, down 5.45 won from the previous session's close. (Yonhap)