The benchmark KOSPI stood at 6,659.29 points at around 10 a.m., up 0.48 percent from the previous session. The index fell 0.06 percent shortly after the market opened to 6,623.33 points before turning higher.
Retail investors bought a net 125.0 billion won (US$92 million) of KOSPI shares. Foreign investors sold a net 365.6 billion won ($269 million), while institutions bought a net 50.4 billion won ($37 million).
Despite the rebound, sentiment remained cautious after four straight sessions of losses left the index at 6,627.26 the previous day. Investors were weighing bargain hunting against persistent pressure from oil prices, bond yields and the prospect of another U.S. rate increase.
Those concerns were reinforced by another weak session on Wall Street. The Dow Jones Industrial Average lost 0.63 percent, while the S&P 500 fell 0.45 percent and the Nasdaq Composite dropped 0.78 percent.
Oil prices remained high on concerns about Middle East supply. Saudi Arabia suspended crude shipments from Yanbu, a major oil-export port on the Red Sea, after a pipeline disruption, while Libya stopped production at three oil fields. November Brent crude rose 2.90 percent to $108.75 a barrel, while October West Texas Intermediate advanced 4.38 percent to $105.83.
The rise in crude added pressure to the bond market. The benchmark U.S. 10-year Treasury yield climbed as high as 5.041 percent, its highest level since July 2007.
Investors remained cautious ahead of the Federal Open Market Committee's decision due early Thursday in Seoul. Futures markets priced in about a 95 percent chance that the Fed would raise rates by 0.25 percentage point, with markets also watching for signs of further tightening.
Still, some technology shares in New York showed signs of stabilization after recent losses. Nvidia gained 0.57 percent, Micron Technology rose 0.39 percent and Advanced Micro Devices advanced 2.19 percent, helping cushion concerns over a recent pullback in artificial intelligence-related stocks.
That strength carried into Seoul's semiconductor sector. SK hynix gained 2.31 percent to 1,729,000 won. Samsung Electronics rose 1.11 percent to 251,250 won, while its preferred shares climbed 4.60 percent to 195,700 won.
Other technology-related shares also advanced. Samsung Electro-Mechanics rose 1.90 percent to 1,342,000 won, while SK Square gained 0.90 percent to 1,009,000 won.
Among other large-cap stocks, battery maker LG Energy Solution climbed 1.64 percent to 371,500 won, while Hyundai Motor fell 1.23 percent to 362,500 won. Samsung Biologics slipped 0.35 percent to 1,407,000 won.
Financial shares edged higher. KB Financial rose 0.34 percent to 176,400 won, while Samsung Life Insurance added 0.18 percent to 286,000 won.
Investors were also digesting the early performance of the Korea Exchange (KRX)'s new after-market session, which began on Monday and runs from 4 p.m. to 8 p.m.
According to the KRX, combined KOSPI and KOSDAQ after-market turnover totaled 1.01 trillion won on Tuesday, down 44.6 percent from 1.82 trillion won on the launch day. Trading volume fell 15.4 percent to 61.1 million shares.
Broader market sentiment remained weak, with the junior KOSDAQ down 1.03 percent at 804.05 as of 9:51 a.m. The index opened at 808.37 and moved between 801.90 and 808.53 in early trading.
Despite the index decline, some of the most actively traded stocks posted gains. Lightron Fiber-Optic Devices, an optical communications equipment maker, jumped 8.37 percent to 4,465 won, while Taihan Fiberoptics rose 4.81 percent to 14,820 won.
VISSEM Electronics, an electronic-components maker, surged 20.93 percent to 12,940 won. Korea Advanced Materials, which makes telecommunications equipment, gained 2.98 percent to 3,460 won.
Security and software shares were also stronger. AXGATE, a system-software company, climbed 2.39 percent to 17,970 won, while Hancom WITH, a digital security company, rose 5.74 percent to 5,530 won.
Elsewhere, semiconductor equipment maker Jusung Engineering slipped 0.47 percent to 191,900 won. Sky Labs, a maker of wearable medical devices, gained 2.16 percent to 21,250 won. Sungho Electronics, an electronic-components maker, advanced 5.77 percent to 17,780 won, while robotics company ROBOTIS fell 5.08 percent to 308,000 won.
The Korean won weakened to 1,371.6 per dollar from 1,359.4 a day earlier.
AJP Takeaways
- South Korea's KOSPI rose 0.48 percent to 6,659.29 as of 10:01 a.m. on September 16, 2026, as gains in Samsung Electronics and SK hynix offset pressure from high oil prices and U.S. Treasury yields.
- Foreign investors sold a net 365.6 billion won ($269 million) of KOSPI shares, while retail investors bought 125.0 billion won ($92 million) and institutions bought 50.4 billion won ($37 million).
- The Korean won weakened to 1,371.60 per dollar from 1,359.40 a day earlier as higher U.S. yields and rate concerns pressured the currency.
Copyright ⓒ Aju Press All rights reserved.
