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 ended lower for the second day in a row Thursday, as uncertainties linger over talks on the United States' debt ceiling to avoid a federal default. The local currency fell against the US dollar.

The benchmark Korea Composite Stock Price Index shed 12.76 points, or 0.5 percent, to close at 2,554.69. Trading volume was moderate at 903.89 million shares worth 9.27 trillion won ($6.99 billion), with losers outpacing gainers 681 to 182.

The index opened slightly higher, despite overnight losses on Wall Street, on the back of gains of chipmakers but turned lower on heavy selling by institutions.

Institutions sold a net 588.89 billion won worth of shares, while retail and foreign investors bought a net 376.54 billion won and 205.68 billion won worth of shares, respectively.

Investors remain wary of the US debt ceiling talks, as there has been little progress, despite US President Joe Biden and House Speaker Kevin McCarthy saying late Monday (local time) that they had a productive meeting.

Eyes were also on the Bank of Korea, as it held interest rates steady at 3.5 percent as widely expected Thursday and cut this year's growth estimate amid the global economic slowdown.

"Coupled with concerns about the US debt ceiling deal, the future policy path of the Federal Reserve has also affected investor sentiment," Kiwoom Securities analyst Han Ji-young said.

According to the minutes of the Fed's latest meeting in May, officials were divided on whether to pause rate hikes at their June rate-setting meeting.

In Seoul, most top-cap shares ended lower, though solid gains of chipmakers limited the fall of the index.

Market bellwether Samsung Electronics rose 0.44 percent to 68,800 won, and chip giant SK hynix spiked 5.94 percent to 103,500 won.

Their rise came after US chip giant Nvidia shares rose by about 25 percent in after-hours trading on a report that booming demand for artificial intelligence processors would fuel revenue growth.

But leading battery maker LG Energy Solution fell 0.34 percent to 583,000 won, and LG Chem tumbled 1.11 percent to 712,000 won. Samsung SDI sank 1.96 percent to 700,000 won.

Major bio firm Samsung Biologics dived 1.64 percent to 779,000 won, and Celltrion sank 3.3 percent to 173,100 won.

Carmakers also lost ground. Top automaker Hyundai Motor skidded 1.93 percent to 203,500 won, and its affiliate Kia slid 2.24 percent to 87,100 won.

No. 1 steelmaker Posco Holdings shed 1.62 percent to 365,000 won, and Posco Future retreated 1.95 percent to 327,000 won.

Among gainers, internet giant Naver advanced 1.48 percent to 206,000 won on bargain hunting, and SK Innovation went up 1.03 percent to 185,700 won.

The local currency ended at 1,326 won against the US dollar, down 8.6 won from the previous session's close. (Yonhap)