South Korean stocks ended markedly lower Wednesday, led by tech losses, as investors took a breather after three days of gains, awaiting the Federal Reserve's interest rate decision. The local currency advanced against the US dollar.

The benchmark Korea Composite Stock Price Index fell 44.10 points, or 1.67 percent, to close at 2,592.36. Trading volume was heavy at 825.02 million shares worth 36.01 trillion won ($28.23 billion), with losers far outpacing gainers 871 to 50.

The index moved within a tight range before turning lower and extending losses on heavy sell-off by foreign investors.

Offshore and institutional investors shed a net 945.96 billion won and 67.51 billion won worth of shares, respectively, while individuals picked up a net 995.47 billion won worth of shares.

"Investors want to check the Federal Reserve's monetary policy direction and its economic outlook," Han Ji-young, an analyst at Kiwoom Securities Co., said.

The Fed began a two-day rate-setting meeting on Tuesday, where the US central bank is largely expected to raise the key rate by 0.25 percentage point.

Investors harbor hopes that this might be the final hike of the Fed's monetary tightening cycle.

In Seoul, most big-cap shares ended lower.

Market bellwether Samsung Electronics fell 0.29 percent to 69,800 won, and leading battery maker LG Energy Solution dropped 2.36 percent to 580,000 won.

SK hynix fell 0.35 percent to 113,000 won after it reported second-quarter losses on sagging demand, though expectations run high for a turnaround in the second half.

But LG Chem grew 0.41 percent to 728,000 won.

Posco shares lost ground following recent sharp gains. Posco Holdings skidded 4.26 percent to 630,000 won, and Posco Future M dropped 6.35 percent to 560,000 won.

Top automaker Hyundai Motor retreated 0.9 percent to 198,700 won after it reported a record high quarterly operating profit on the back of the popularity of its high-end models and a weak won.

Its affiliate Kia dived 2.36 percent to 82,600 won.

Among decliners, major bio firm Samsung Biologics decreased 1.09 percent to 727,000 won, and internet giant Naver lost 1.64 percent to 197,700 won. Kakao, the operator of the popular mobile messenger KakaoTalk, sank 2.15 percent to 47,800 won.

The local currency ended at 1,274.5 won against the US dollar, up 0.9 won from the previous session's close. (Yonhap)