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SEOUL, Oct. 15 (Yonhap) -- South Korean stocks plunged more than 7 percent Thursday as major chipmakers extended losses amid growing concerns over the sustainability of investments related to artificial intelligence (AI) and rate hikes by the Federal Reserve. The Korean won weakened against the U.S. dollar.
After opening 5.59 percent lower, the benchmark Korea Composite Stock Price Index (KOSPI) extended its losses, tumbling 454.59 points, or 7.57 percent, to end at 5,554.22, after dipping as low as 5,450.81.
The KOSPI fell for the seventh consecutive session, marking its longest losing streak since September 2024. Thurday's closing price was the lowest since April 7, when the index fell below 5,500.
The sharp sell-off prompted the Korea Exchange (KRX) to activate a sell-side sidecar shortly after the market opened, suspending program selling for five minutes as KOSPI 200 futures fell more than 5 percent for at least one minute.
As losses deepened, the bourse operator activated a circuit breaker at 12:38 p.m., halting trading on the main bourse for 20 minutes after the KOSPI dropped more than 8 percent from the previous session's close.
Overnight, U.S. stocks closed lower as renewed concerns over the sustainability of AI-related spending and hotter-than-expected September inflation data dampened investor sentiment.
The U.S. Consumer Price Index (CPI) rose 0.6 percent on month in September, its fastest monthly increase since April, fueling concerns that persistent inflation could prod the Fed to raise interest rates.
Financial data is displayed on a screen inside the dealing room of Hana Bank in central Seoul on Oct. 15, 2026, after the market closed. (Yonhap)
Trade volume was moderate at 363.47 million shares worth 26.87 trillion won (US$19.97 billion), with decliners far outnumbering advancers 787 to 112.
Foreigners sold a net 3.62 trillion won, while institutions and individuals bought a net 1.69 trillion won and 1.29 trillion won, respectively.
"The KOSPI market came under heavy selling pressure amid concerns over the sustainability of AI-related investments, intensifying competition in memory chip production and rising borrowing costs," Lee Kyoung-min, an analyst at Daishin Securities, said.
"Semiconductor shares slumped, while IT hardware and power equipment stocks also declined as investor sentiment toward the broader AI value chain weakened," he added.
Market heavyweights fell across the board, led by a sharp sell-off in technology shares.
Market bellwether Samsung Electronics plunged 9.48 percent to 210,000 won, while chip giant SK hynix tumbled 11.06 percent to 1.26 million won.
SK Square, the parent firm of SK hynix, dipped 10.21 percent to 765,000 won, while Samsung Electro-Mechanics, an electronics component affiliate of Samsung Electronics, sank 15.36 percent to 1.16 million won.
The Korean won was quoted at 1,344.6 won against the U.S. dollar as of 3:30 p.m., down 2.3 won from the previous stock trading session's close.
Bond prices, which move inversely to yields, closed higher. The yield on three-year Treasurys shed 1.6 basis points to 3.867, and the return on the benchmark five-year government bonds lost 4 basis points to 4.007.
ejkim@yna.co.kr
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