South Korean stocks ended down for the fifth straight session on Monday as investors remained worried over the impact of the emergence of the omicron variant of the coronavirus on the global economy. The Korean won rose against the US dollar.

The benchmark Korea Composite Stock Price Index (Kospi) retreated 27.12 points, or 0.92 percent, to close at 2,909.32 points.

Trading volume was moderate at about 832 million shares worth some 12.9 trillion won (US$10.8 billion), with losers outnumbering gainers 831 to 78.

Foreigners bought a net 39 billion won and institutions purchased 715 billion won, while retail investors sold 756 billion won.

The Kospi dipped below the 2,900-point level in the early morning, driven by investors' worries that the outbreak of the new COVID-19 variant may roll back recently eased quarantine measures and hamper the economic recovery at home and overseas.

"Omicron is the largest volatility factor at the moment, and investors seem to be anxious about the absence of concrete information (about the virus' impact)," Kiwoom Securities analyst Kim Sae-hun said.

Earlier in the day, South Korea reported 3,309 new COVID-19 cases, though none of them have been confirmed as an infection from the omicron variant.

The main stock index pared the losses later as foreign and institutional investors picked up oversold shares.

Most large caps closed lower in Seoul, while financial and bio shares performed well.

Market bellwether Samsung Electronics closed flat at 72,300 won, and No. 2 chipmaker SK hynix added 0.43 percent to 116,000 won.

Leading carmaker Hyundai Motor declined 2.43 percent to 200,500 won, and steelmaker Posco decreased 2.76 percent to 264,500 won. Internet portal operator Naver declined 0.77 percent to 386,500 won.

Pharmaceutical giant Samsung Biologics gained 1.61 percent to 884,000 won, banking top cap Kakao Bank increased 3.08 percent to 70,300 won, and payment service provider Kakao Pay surged 7.19 percent.

The local currency closed at 1,193 won against the US dollar, up 0.3 won from the previous session's close. (Yonhap)