An electronic board showing the Korea Composite Stock Price Index at a dealing room of the Hana Bank headquarters in Seoul on Tuesday. (Yonhap)

South Korean stocks opened almost flat Tuesday as investors awaited a key US inflation report set to be released later this week.

The benchmark Korea Composite Stock Price Index gained 0.51 point, or 0.02 percent, to 2,727.72 in the first 15 minutes of trading.

Overnight, the S&P 500 closed almost flat, while the Dow Jones Industrial Average fell 0.2 percent. The tech-heavy Nasdaq composite gained 0.3 percent.

Investors' eyes are on the US Consumer Price Index data for April due out Wednesday, which will give clues for the future course of the Federal Reserve's key rate decision.

In Seoul, tech behemoth Samsung Electronics shed 0.26 percent, and No. 2 chipmaker SK hynix dropped 0.33 percent.

Financial shares also lost ground, with KB Financial Group plunging 3.68 percent and Hana Financial Group retreating 1.73 percent.

Battery and auto shares gained ground.

Leading battery maker LG Energy Solution gained 0.66 percent, Samsung SDI edged up 0.12 percent and Posco Future M climbed 1.45 percent.

Top automaker Hyundai Motor increased 0.41 percent, and its smaller affiliate Kia went up 0.35 percent.

Internet portal operator Naver also advanced 1.25 percent, and Kakao, the operator of the country's top mobile messenger, grew 0.53 percent.

The local currency was trading at 1,368.20 won against the US dollar, unchanged from the previous session's close. (Yonhap)