Seoul stocks closed almost flat Wednesday as investors await the release of US inflation data later this week. The Korean won declined against the dollar.

After choppy trading, the benchmark Korea Composite Stock Price Index closed up 2.78 points, or 0.11 percent, to 2,550.64.

Institutional and retail investors were net sellers and sold off a combined 234.9 billion won ($176.9 million), while foreigners snapped up a net 212.8 billion won.

The main index moved between gains and losses, as investors remained cautious ahead of the release of the March readings of the consumer price index, due Wednesday, which will offer hints to the Fed's monetary tightening policy path.

"Investors locked in profits in the battery and semiconductor stocks, ahead of the US CPI data and the release of the March FOMC minutes," said analyst Seo Sang-yong from Mirae Asset Securities.

In Seoul, large-cap shares closed mixed with autos rising and chemicals suffering losses.

Market bellwether Samsung Electronics inched up 0.15 percent to 66,000 won, while rival SK hynix retreated 1.63 percent to 90,300 won.

Auto shares gathered ground. Industry leader Hyundai Motor climbed 3.18 percent to 198,200 won, while its sister affiliate Kia added 1.29 percent to 86,100 won.

Posco Holdings, the country's top steelmaker, advanced 2.39 percent to 406,500 won.

Among decliners, portal operator Naver was down 0.95 percent to 198,000 won, refinery SK Innovation dipped 4.83 percent to 193,200 won, and battery maker LG Energy Solution fell 3.28 percent to 590,000 won.

The local currency closed at 1,325.7 won against the greenback, down 3.5 won from the previous session's close. (Yonhap)