[DigitalToday reporter Sangyeop Oh] The KOSPI fell more than 5 percent shortly after the open, sliding to the 5,600 level. Foreign investors were net sellers by more than 280 billion won early in the session, while large-cap stocks including Samsung Electronics and SK Hynix fell across the board, triggering a sell-side sidecar on the main board.

As of 9:03 a.m. on Oct. 15, the KOSPI was down 319.37 points, or 5.32 percent, at 5,689.44 from the previous session. The index opened at 5,673.01, down 335.80 points, or 5.59 percent, from the prior close.

The Korea Exchange triggered a sell-side sidecar on the main board at 9:07:42 a.m. due to the sharp fall in the index. Program sell orders were suspended for 5 minutes after the KOSPI 200 futures price fell 49.68 points, or 5.27 percent, to 892.58 from the reference price of 942.26.

Foreign investors led the fall, net selling 285.6 billion won. Retail investors also net sold 16.0 billion won, while institutions net bought 296.6 billion won.

Most top market-cap stocks also plunged. Samsung Electronics was down 6.03 percent at 218,000 won, while SK Hynix fell 7.61 percent to 1,311,000 won.

Elsewhere, SK Square fell 7.98 percent, Samsung Electro-Mechanics dropped 9.75 percent, Hyundai Motor slipped 4.94 percent, Samsung Life fell 4.67 percent and LG Energy Solution lost 3.55 percent. KB Financial and Samsung Biologics were down 2.14 percent and 1.61 percent, respectively.

The KOSDAQ also fell below 800. At the same time, the index was down 38.95 points, or 4.73 percent, at 784.93 from the previous session.

The won was at 1,340.40 per dollar, up 2.60 won from the previous session.

Domestic stocks are undergoing further correction as weakness in U.S. AI-related shares and macro uncertainty overlap, despite a continuing string of declines through the previous day. The KOSPI rebounded more than 2 percent early the previous day, but gave up all gains on foreign selling and ended down 0.44 percent at 6,008.81.

Han Ji-young (한지영), a researcher at Kiwoom Securities, said the domestic stock market was expected to start weaker due to concerns over U.S. inflation data and the spillover from a sharp fall in U.S. AI infrastructure shares. She also said the market could pare losses as it digests the possibility of technical buying after the recent string of steep declines and an earnings announcement scheduled later in the session from TSMC.