South Korean stocks opened steeply lower Thursday after the three-day Chuseok holiday, following comments by the US Federal Reserve's chief that it could start tapering its stimulus as early as November and growing woes over a default of a giant Chinese real estate developer.

The benchmark Korea Composite Stock Price Index (KOSPI) fell 17.83 points, or 0.57 percent, to 3,122.68 points in the first 15 minutes of trading.

The key stock index plunged as investors digest the overnight US FOMC meeting results that it could begin reducing its asset-buying program in November and finish the process by next year.

Investors also kept a close eye on the debt fiasco at China's Evergrande Group, one of the country's largest property developers, that has increased volatility in the global financial markets for the past few days.

South Korea's exports increased 22.9 percent on-year in the first 20 days of September on robust demand for chips, petroleum products and autos.

Top cap Samsung Electronics slipped 0.13 percent, and No. 2 chipmaker SK hynix retreated 0.93 percent.

Internet portal operator Naver moved down 0.74 percent, and pharmaceutical giant Samsung Biologics decreased 0.43 percent.

Leading chemical firm LG Chem added 2.43 percent, while top automaker Hyundai Motor declined 1.2 percent. Top bank stock Kakao Bank lost 1.62 percent.

The local currency was trading at 1,184.1 won against the US dollar, down 9.1 won from the previous session's close. (Yonhap)