South Korean stocks closed slightly lower on Wednesday, slipping from their almost two-year highs the previous session, as investors opted to lock in part of recent gains ahead of the outcome of the Federal Reserve's rate policy meeting. The Korean won rose to the US dollar.

The benchmark Korea Composite Stock Price Index shed 0.78 point, or 0.04 percent, to close at 2,133.00. Trade volume was moderate at 370 million shares worth 4.81 trillion won ($4.21 billion), with losers outnumbering gainers 516 to 285.

The local stock market opened a tad lower as investors cashed in recent gains and took to the sidelines ahead of the outcome of the Fed's announcement on its rate policy.

The KOSPI has been on a steady rise as foreign investors continued to scoop up local stocks, extending their buying binge to an eighth consecutive day following eased political chaos in Asia's fourth-largest economy and sound economic data.

Adding to this, market uncertainties eased after the Constitutional Court ruled last week to oust now former President Park Geun-hye.

Park was impeached by parliament on Dec. 9 on allegations she let a close friend meddle in state affairs, colluding with her to extort money from conglomerates and others.

"A slide in oil prices have led to a fall in the US stock market, and investors remained cautious as the Fed is set to announce its rate decision," said Lee Kyong-min, an analyst at Daishin Securities.

Most market heavyweights closed higher with banking and tech stocks leading market gains.

Foreign investors snatched up a net 121 billion won worth of local stocks, extending their buying streak to an eighth day, while institutional investors offloaded a net 259 billion won.

Top cap Samsung Electronics edged up 0.1 percent to end at a fresh record high of 2,070,000 won.

But other affiliates declined following a surge a day before.

On Tuesday, they soared on news that the nation's largest business group remains firm in pushing for a plan to transition to a holding company structure, regardless of the leadership vacuum caused by the detention of its de facto chief, Lee Jae-yong.

Samsung C&T, the de facto holding firm of Samsung, shed 0.76 percent to end at 131,000 won, and Samsung Life Insurance, the group's non-life insurer, also fell 0.44 percent to end at 113,500 won.

Hyundai Motor, the country's leading automaker, gained 0.34 percent at 149,500 won, and SK hynix, a major chipmaker, shed 2.98 percent to 48,800 won.

LG Electronics, a major home appliance maker, was 1.04 percent higher at 67,800 won on hopes that its latest high-end smartphone, the G6, will sell more than expected.

SK Telecom, the No. 1 mobile carrier, advanced 4.89 percent to end at 257,500 won.

Banking stocks ended their bullish runs seen in the past few sessions. KB Financial declined 0.39 percent to end at 51,400 won, while Shinhan Financial fell 0.6 percent to end at 49,400 won.

The local currency closed at 1,143.60 won against the US dollar, up 5.2 won from the previous session's close.

Bond prices, which move inversely to yields, closed mixed. The yield on three-year Treasurys rose 0.1 basis point to 1.759 percent, while the return on the benchmark five-year government bonds fell 1.2 basis points to 1.978 percent. (Yonhap)