South Korean shares closed almost flat Wednesday ahead of US tech giant Nvidia's closely watched earnings announcement. The local currency fell against the US dollar.

The benchmark Korea Composite Stock Price Index gained 0.58 points, or 0.02 percent, to close at 2,689.83.

Trade volume was moderate at 276.4 million shares worth 10.4 trillion won ($7.77 billion). Losers, however, outnumbered winners 625 to 260.

Institutions sold a net 33.9 billion won worth of shares, while individuals and foreign investors combined bought a net 30.7 billion won.

Kim Ji-won, an analyst at KB Securities, said: "There is a mix of anticipation and caution regarding Nvidia's earnings. The company's second-quarter performance and its future outlook are expected to significantly impact the stock market."

"The domestic market is likely to lean toward a wait-and-see stance," Kim added.

Tech stocks finished higher after trading mostly lower throughout the session.

Top cap Samsung Electronics added 0.79 percent to close at 76,400 won, and chip rival SK hynix rose 2.46 percent to 179,300 won.

Bio-related shares also advanced, with Samsung Biologics climbing 1.85 percent to 991,000 won and Celltrion rising 0.5 percent to 201,500 won.

Automakers also enjoyed brisk trading, with industry leader Hyundai Motor soaring 4.65 percent to 259,000 won and affiliate Kia rising 2.75 percent to 201,500 won.

In contrast, energy shares retreated, with leading refiner SK Innovation down 2.73 percent to 106,800 won and S-Oil also falling 1.41 percent to 62,900 won.

The local currency had been trading at 1,339 won against the dollar as of 3:30 p.m., down 8 won from the previous session. (Yonhap)