Samsung Electronics, SK Hynix tumble after two-day rally; Kospi falls over 4% to 6,300s

The Kospi fell more than 4 percent in early trading Thursday, dragged down by weakness in large-cap semiconductor stocks, while the Kosdaq turned lower for the first time in five sessions.

As of 9:57 a.m., the Kospi was down 4.03 percent at 6,332.26.

The index opened 1.81 percent lower at 6,478.75 before extending its losses, at one point sliding to 6,328.94. The Kospi had risen 3.76 percent on Wednesday, marking a second consecutive day of gains, but reversed course Thursday for the first time in three sessions.

Foreign investors were net sellers of 893.9 billion won ($627 million), while retail and institutional investors were net buyers of 787.6 billion won and 79.4 billion won, respectively.

Overnight on Wall Street, major indexes posted a mixed session as markets showed signs of fatigue after a four-session rally fueled by expectations that the Strait of Hormuz would reopen.

The Dow Jones Industrial Average rose 0.49 percent, while the S&P 500 and the Nasdaq Composite fell 0.17 percent and 0.83 percent, respectively.

AI chipmaker Nvidia gained 3.44 percent after SpaceX announced it would use only Nvidia chips for its data center infrastructure buildout. Advanced Micro Devices slid 7.04 percent after its forward sales outlook fell short of market expectations.

The Philadelphia Semiconductor Index fell 1.40 percent as a result, snapping a four-session winning streak.

Alphabet also dropped 4.06 percent after news broke that Jeff Dean, a scientist widely regarded as a legend within Google, was leaving the company.

Domestic stocks came under selling pressure in tandem with the weakness in US semiconductor shares. Profit-taking also emerged after the Kospi's two consecutive sessions of gains.

Among the top market-cap stocks, Samsung Electronics and SK Hynix — both of which had risen for two straight sessions — led the index lower with sharp declines.

Samsung Electronics was trading down 4.78 percent at 234,250 won, while SK Hynix fell 8.69 percent to 1.523 million won.

SK Square and Samsung Electro-Mechanics also tumbled more than 10 percent, falling 10.72 percent and 10.32 percent, respectively.

The Kosdaq was also down 1.23 percent at 789.72 at the same time, turning lower for the first time in five sessions since July 30.

The Kosdaq had opened 0.27 percent lower at 797.44, briefly turned positive and recovered the 800 level, before reversing course again.

Foreign and institutional investors were net sellers of 158.9 billion won and 13.9 billion won, respectively, while retail investors were net buyers of 172.7 billion won. Top market-cap stocks showed a mixed performance.

Han Ji-young, an analyst at Kiwoom Securities, said the market's upward momentum would stall Thursday despite improvements in geopolitical and macroeconomic conditions, citing weakness in US semiconductor stocks and profit-taking following the recent sharp rebound. "The market will likely see a 'breather' session characterized by sector rotation," Han said.