Stocks decline 0.9% to fall below 3,100 level
The benchmark Kospi fell 27.87 points, or 0.9 percent, to close at 3,079.75 points.
Trading volume was moderate at about 1.8 billion shares worth some 18 trillion won ($16.2 billion), with losers outnumbering gainers 510 to 339.
Foreigners sold a net 321 billion won, and institutions offloaded a net 458 billion won, while retail investors purchased a net 749 billion won.
The key stock index started with mild gains, as Korea's exports rose 16.7 percent on-year in the first 20 days of February on strong shipments of chips and autos.
Stocks fell, however, as foreigners sold for the fourth consecutive session amid lingering concerns over the U.S. Treasury yields hike, generated by signs of global economic rebound from the pandemic.
"The combined foreign and institutional selling kept the Kospi down," Kiwoom Securities analyst Seo Sang-young said.
"The local stock markets remain under selling pressure by the People's Bank of China's liquidity squeeze," he said.
In Seoul, most large caps closed lower.
Samsung Electronics lost 0.48 percent to 82,200 won, while chipmaker SK hynix gained 2.63 percent to 136,500 won.
Samsung Biologics declined 1.64 percent to 780,000 won, and Celltrion dropped 2.83 percent to 309,500 won.
Internet portal giant Naver shed 2.89 percent to 386,500 won, with its rival Kakao dipping 2.68 percent to 490,500 won.
Online game maker NCSoft lost 6.62 percent to 931,000 won, while its rival Netmarble dropped 3.05 percent to 127,000 won.
Chemical maker LG Chem fell 2.66 percent to 916,000 won, and rechargeable battery maker Samsung SDI retreated 4.03 percent to 739,000 won.
Hyundai Motor, the country's largest automaker, slipped 0.21 percent to 241,500 won, while steelmaker Posco advanced 1.71 percent to 268,000 won.
The Kosdaq dropped 10.82 points, or 1.12 percent, to close at 954.29.
The local currency closed at 1,110.4 won per dollar, up 4.5 won from the previous session's close.
Bond prices, which move inversely to yields, closed lower. The yield on the three-year bond added 2.3 basis points to close at 1.02 percent, and the yield on the 10-year bond gained 4.1 basis points to close at 1.33 percent.
BY CHEA SARAH, YONHAP [firstname.lastname@example.org]