South Korean stocks tumbled by more than 2 percent to dip below the 3,000-point threshold Wednesday on massive foreign selling, largely due to concerns over a US bond yield hike that drove the key stock index down for the past few sessions. The Korean won fell against the US dollar.

The benchmark Korea Composite Stock Price Index (KOSPI) dipped 75.11 points, or 2.45 percent, to close at 2,994.98 points.

Trading volume was moderate at about 1.5 billion shares worth some 16.7 trillion won ($17.7 billion), with losers outnumbering gainers 835 to 57.

Foreigners sold a net 427 billion won, while retail investors purchased a net 560 billion won. Institutions offloaded a net 134 billion won.

"The increase in foreign sell-offs raised uncertainties," said Kiwoom Securities analyst Seo Sang-young.

Investor concerns grew as optimism for quick global recovery spurred speculation for rate hikes.

Foreign selling continued despite the Federal Reserve chairman's overnight comments that the Fed would continue its fiscal policy support.

In Seoul, most large caps closed lower.

Market bellwether Samsung Electronics closed unchanged at 82,000 won, and No. 2 chipmaker SK hynix shed 1.81 percent to 136,000 won.

Top pharmaceutical firm Samsung Biologics lost 1.71 percent to 747,000 won, and Celltrion dipped 4.73 percent to 282,000 won.

Internet portal giant Naver retreated 4.23 percent to 374,000 won, with its rival Kakao dipping 2.77 percent to 473,500 won.

Battery makers and automakers dropped after Hyundai Motor said it will replace batteries in over 25,000 Kona electric vehicles (EVs) due to defects in battery cells.

Hyundai Motor, the country's largest automaker, moved down 3.89 percent to 235,000 won.

Leading chemical maker LG Chem, whose batteries were used in Kona EVs, fell 2.82 percent to 860,000 won, and rechargeable battery maker Samsung SDI dropped 3.24 percent to 687,000 won.

The local currency closed at 1,112.2 won per dollar, down 1.6 won from the previous session's close.

Bond prices, which move inversely to yields, closed higher. The yield on three-year Treasurys lost 1.4 basis points to 1.006 percent, and the return on the benchmark five-year government bond fell 3 basis points to 1.356 percent. (Yonhap)