South Korean stocks closed sharply lower on Monday, as disappointment over Samsung Electronics' shareholder return plan triggered a sell-off in the semiconductor sector, while the Korean won strengthened against the U.S. dollar. The benchmark KOSPI index fell 215.99 points, or 3.12%, to close at 6,696.96 points.

Trading volume was thin, with 264.9 million shares changing hands, amounting to 26.1 trillion Korean won (approximately $18.9 billion). Advancers outnumbered decliners, with 576 stocks rising and 286 falling. The index opened lower and extended losses as large-cap technology stocks faced selling pressure from foreign and institutional investors, who recorded a combined net sell-off of 4.97 trillion won, while retail investors bought a net 3.32 trillion won.

“The shareholder return plan announced by Samsung Electronics last week fell short of market expectations, dragging down the KOSPI, and shares of Samsung-affiliated companies also weakened broadly,” said Lee Kyung-min, an analyst at Daishin Securities. The chip giant unveiled a return program worth between 90 trillion and 110 trillion Korean won (approximately $652 billion) on Friday, with plans to distribute around 30 trillion won in cash dividends for the third quarter. However, the exact amount and details will be finalized at a board meeting in October.

The analyst added that while the overall scale of the return is substantial, Samsung did not disclose specific details regarding share buybacks, leaving investors disappointed. Most blue-chip stocks closed lower. Market heavyweight Samsung Electronics tumbled 8.7% to 257,000 won, while rival SK Hynix fell 3.41% to 1,671,000 won. Financial institution KB Financial Group slipped 0.73% to 163,100 won, leading automaker Hyundai Motor retreated 0.24% to 414,000 won, and nuclear power equipment maker Doosan Energy declined 0.41% to 73,000 won.