The benchmark KOSPI stood at 6,847.74 as of 10:30 a.m., down 2.63percent from the previous session. The Nikkei 255 was also down 2.66 percent to 63,554.48.
The KOSPI opened more than 3 percent lower at 6,802.50 before paring some of its losses in early trading as retail investors stepped in to buy shares.
Retail investors bought a net 1.32 trillion won ($979 million) of KOSPI shares. Foreign investors sold a net 844.6 billion won, while institutions unloaded 760.1 billion won.
The decline followed another weak session in New York as higher oil prices and bond yields weighed on risk assets. The Dow Jones Industrial Average fell 0.60 percent overnight and the S&P 500 lost 0.58 percent. The Nasdaq Composite dropped 0.65 percent.
West Texas Intermediate crude surged 6.69 percent to $102.48 a barrel, while Brent crude jumped 6.34 percent to $107.63. Both benchmarks closed at their highest levels since May 19. WTI extended its gains for an eighth straight session, marking its longest winning streak in three years.
The surge in oil prices added to inflation concerns, contributing to broader pressure on the bond market as U.S. Treasury yields moved sharply higher. The benchmark 10-year Treasury yield briefly rose above 4.95 percent, reaching its highest level since November 2023. The jump in yields weighed particularly on rate-sensitive technology shares, while investors remained cautious ahead of the U.S. August consumer price index due later Friday.
Semiconductor stocks were hit particularly hard on Wall Street. Nvidia fell 2.26 percent and Micron Technology dropped 4.90 percent. The Philadelphia Semiconductor Index declined 2.66 percent.
That weakness carried into Seoul, where major chip stocks led the morning decline. Samsung Electronics fell 3.53 percent to 259,500 won, while SK hynix dropped 3.62 percent to 1,786,000 won. Samsung Electronics preferred shares lost 4.43 percent to 194,000 won.
Other semiconductor-related shares were also weaker. SK Square fell 4.23 percent to 1,087,000 won, while Samsung Electro-Mechanics bucked the trend and rose 0.86 percent to 1,412,000 won.
Losses extended to other large-cap stocks. LG Energy Solution fell 1.37 percent to 360,000 won and Hyundai Motor dropped 2.25 percent to 380,250 won. Samsung Biologics slipped 0.84 percent to 1,411,000 won.
Financial shares were mixed. KB Financial gained 1.01 percent to 175,150 won, while Samsung Life Insurance fell 2.91 percent to 300,500 won.
Some industrial and construction shares, however, moved higher. GS E&C rose 3.49 percent to 38,550 won and HD Hyundai Heavy Industries advanced 2.54 percent to 465,000 won.
Selling was broad across the main market. A total of 551 KOSPI-listed stocks declined, while 276 advanced and 67 were unchanged.
The junior KOSDAQ also came under pressure, falling 1.72 percent to 822.55. Retail investors bought a net 158.1 billion won, while foreign investors sold 111.5 billion won and institutions offloaded 46.7 billion won.
Losses were broad across major KOSDAQ names.
Biotech company Alteogen fell 2.71 percent to 269,500 won, while battery materials makers EcoPro and EcoPro BM which specializes in cathode materials for rechargeable batteries dropped 2.76 percent to 84,500 won and 4.21 percent to 113,700 won, respectively. EcoPro BM specializes in cathode materials for rechargeable batteries.
Semiconductor equipment and component shares were also weaker. Jusung Engineering slipped 0.23 percent to 220,500 won and Wonik IPS fell 5.47 percent to 112,300 won. EO Technics, a maker of semiconductor laser equipment, dropped 3.30 percent to 440,000 won. LEENO Industrial declined 4.04 percent to 66,500 won, while printed circuit board maker Simmtech lost 2.02 percent to 131,200 won.
Robotics shares were mostly lower. Industrial robot maker Rainbow Robotics fell 2.23 percent to 439,000 won.
Robotis was the only gainer among the major names shown, rising 0.46 percent to 325,000 won.
Market breadth was firmly negative, with 1,126 KOSDAQ stocks declining, compared with 484 advancing and 112 unchanged.
The Korean won weakened to 1,346.50 per dollar from 1,339.20 a day earlier.
Investors are now focused on the U.S. August consumer price index, due later Friday, for clues on the Federal Reserve's rate outlook ahead of next week's policy meeting. Markets are currently pricing in about a 70 percent chance of a rate increase after August producer prices reinforced concerns over persistent inflation.
AJP Takeaways
- South Korea’s benchmark KOSPI fell below 6,900 on September 11, 2026, as surging oil prices and rising U.S. Treasury yields triggered broad risk-off selling and pushed semiconductor shares sharply lower.
- The KOSPI traded at 6,861.44 as of 10:04 a.m. on September 11, down 2.45 percent, after opening more than 3 percent lower at 6,802.50. Retail investors bought a net 1.32 trillion won ($979 million), while foreign and institutional investors were net sellers.
- West Texas Intermediate crude rose 6.69 percent to $102.48 a barrel and Brent crude climbed 6.34 percent to $107.63 on September 10, while the U.S. 10-year Treasury yield briefly exceeded 4.95 percent. Investors are awaiting the U.S. August consumer price index on September 11, 2026, for further clues on the Federal Reserve’s rate outlook.
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