South Korean stocks slumped on Wednesday, retreating from the previous session's all-time high, as foreign investors remained net sellers. The Korean won declined against the US dollar.

The benchmark Korea Composite Stock Price Index declined 9.39 points, or 0.39 percent, to close at 2,382.56. Trade volume was moderate at 340 million shares worth 5.79 trillion won ($5.06 billion). 

The local stock market opened lower with subdued sentiment after a key vote on US President Donald Trump's health care reform was delayed, rekindling worries about Trump's economic policies.

Foreign investors sold a net 246.2 billion won worth of local stocks.

Kim Dae-jun, a senior research at Hankook Investment & Securities, said foreign investors "intensively" sold large-cap stocks after US Federal Reserve Chair Janet Yellen voiced support for a gradual increase of US interest rates.

Top cap Samsung Electronics fell 1.24 percent to end at 2,385,000 won, and SK hynix, a global chipmaker, slipped 2.89 percent to 67,200 won.

Naver, the operator of the country's top Internet portal, shed 0.92 percent to 861,000 won.

Automakers also finished in negative terrain, with industry leader Hyundai Motor down 0.31 percent to 160,000 won, and its smaller affiliate Kia Motors dipping 0.39 percent to 37,850 won.

The local currency closed at 1,144.00 won against the US dollar, down 7.1 won from the previous session's close.

Bond prices, which move inversely to yields, closed sharply lower. The yield on three-year Treasurys gained 3.0 basis points to 1.711 percent and the return on the benchmark five-year government bond added 5.1 basis points to 1.904 percent. (Yonhap)