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

South Korean stocks fell slightly Thursday following the US Federal Reserve's decision to hold the key rate flat. The Korean won rebounded against the US dollar.

The benchmark Korea Composite Stock Price Index lost 8.41 points, or 0.31 percent, to 2,683.65, ending the three-session winning streak that started last Friday.

Trade volume was slim at 342.7 million shares worth 8.9 trillion won ($6.5 billion). Decliners outnumbered gainers 513 to 357.

Individual and foreign investors bought a net 147.4 billion won worth of local shares, offsetting a net sale of 144.1 billion won by institutions.

"The Korean financial market was slightly weak due to a less-than-expected hawkish stance by the US Federal Reserve," said Lee Jae-won, an analyst at Shinhan Securities.

Overnight, the US central bank kept the rate unchanged for the sixth straight meeting as widely expected due to still high inflation. But the Fed showed a dovish stance, as Fed Chair Jerome Powell said it is "unlikely" for the Fed to make an interest rate hike at its next meeting.

In Seoul, major shares closed mixed.

Tech behemoth Samsung Electronics rose 0.65 percent to 78,000 won, but its chipmaking rival SK hynix fell 0.34 percent to 173,600 won.

Top steelmaker Posco Holdings declined 1.48 percent to 399,000 won, and leading zinc smelter Korea Zinc dropped 0.76 percent to 460,000 won.

Bank shares were negative as Hana Financial Group decreased 2.9 percent to 57,000 won, and KB Financial Group slid 4.37 percent to 72,300 won.

But defense companies finished higher on a strong first-quarter performance as Hanwha Aerospace advanced 4.26 percent to 220,500 won, and Korea Aerospace Industries jumped 4.44 percent to 54,100 won.

Hybe, a record label behind K-pop superstars, dipped 0.99 percent to 200,000 won after releasing its weak first-quarter earnings report amid an internal power struggle.

The local currency closed at 1,375.9 won against the US dollar, up 6.1 won from the previous session's close. (Yonhap)