South Korean stocks ended markedly higher Monday to extend their winning streak to a sixth session as investors were optimistic about a deal on the United States' debt ceiling to avoid a federal default. The local currency rose against the US dollar.

The benchmark Korea Composite Stock Price Index added 19.29 points, or 0.76 percent, to close at 2,557.08. Trading volume was a bit slim at 583.13 million shares worth 8.04 trillion won ($6.09 billion), with gainers outpacing decliners 634 to 235.

The index opened slightly higher and had extended gains on foreign and institutional buying.

Institutions and overseas investors bought a net 534.03 billion won and 246.32 billion won worth of shares, respectively, while retail investors sold a net 787.95 billion won worth of shares.

Eyes are on the upcoming talks between US President Joe Biden and House Speaker Kevin McCarthy on Monday to seek a breakthrough regarding their debt ceiling negotiations after the talks fell through last week.

Investors also watched the monetary policy direction by the Federal Reserve.

Fed Chair Jerome Powell said last week that interest rates may not have to rise as much as expected to quell inflation. Experts widely expect the Fed to take a break from its aggressive tightening in its June rate-setting meeting.

"Despite lingering uncertainties in the macroeconomic circumstances, investors expect a turnaround in the semiconductor market and its impact on the sentiment," Kiwoom Securities analyst Han Ji-young said.

In Seoul, tech and auto shares led the upturn of the index.

Samsung Electronics rose 0.15 percent to 68,500 won, and chip giant SK hynix jumped 0.92 percent to 98,200 won.

Leading battery maker LG Energy Solution surged 1.45 percent to 560,000 won, and LG Chem added 0.29 percent to 700,000 won. Samsung SDI also went up 0.29 percent to 700,000 won.

Carmakers rose, with top automaker Hyundai Motor advancing 0.97 percent to 207,500 won and its affiliate Kia rising 0.11 percent to 88,900 won.

Major bio shares gathered ground. Samsung Biologics surged 1.03 percent to 787,000 won, and Celltrion soared 2.3 percent to 177,900 won.

No. 1 steelmaker Posco Holdings also climbed 1.23 percent to 369,000 won.

But internet giant Naver fell 0.69 percent to 215,000 won, and Kakao, the operator of the popular mobile messenger KakaoTalk, remained unchanged at 57,900 won.

The local currency ended at 1,318.1 won against the US dollar, up 8.6 won from the previous session's close. (Yonhap)