Seoul shares surged by more than 6 percent Wednesday, led by a rally in chipmakers after SK hynix reported record quarterly earnings and announced additional shareholder returns. The Korean won weakened against the US dollar.
The benchmark Korea Composite Stock Price Index gained 374.1 points, or 6.63 percent, to close at 6,012.44, after rising as high as 6,032.28.
As the market rallied on tech gains, the Korea Exchange activated a buy-side sidecar shortly before 11 a.m., suspending program trading buy orders for KOSPI-listed stocks for five minutes.
The measure is triggered when KOSPI 200 futures rise at least 5 percent and stay at that level for at least one minute. It was activated for the second straight session.
Earlier in the day, SK hynix reported record-high revenue and operating profit for the third quarter on robust memory chip demand amid the artificial intelligence (AI) boom. The world's second-largest memory chip maker announced a shareholder return program worth more than 100 trillion won ($75.3 billion) for 2026.
Investors were also awaiting the Federal Reserve's interest rate decision scheduled for early Thursday (Korean time), looking for signals on the future path of US interest rates.
Trade volume was light at 223.2 million shares worth 19.83 trillion won, with advancers outnumbering decliners 580 to 288.
Foreigners and institutions bought a net 815.83 billion won and 960.79 billion won, respectively, while individuals sold a net 1.8 trillion won.
"SK hynix demonstrated that strong demand for AI chips can translate into solid operating profits and shareholder returns, easing concerns about the sustainability of the AI-driven rally and a potential peak in the memory chip cycle," Lee Jae-won, an analyst at Yuanta Securities, said.
Market heavyweights rose across the board.
Top market cap Samsung Electronics jumped 9.01 percent to 242,000 won, and chip giant SK hynix soared 10.89 percent to 1.49 million won.
SK Square, the parent firm of SK hynix, advanced 11.23 percent to 921,000 won, and Samsung Electro-Mechanics, an electronics component affiliate of Samsung Electronics, surged 8.74 percent to 1.3 million won.
The Korean won was trading at 1,337.7 won against the US dollar at 3 30 p.m., down 10.7 won from the previous session's close.
Bond prices, which move inversely to yields, closed lower. The yield on three-year Treasurys gained 4.1 basis points to 3.799, and the return on the benchmark five-year government bonds added 5 basis points to 3.949. (Yonhap)
