SEOUL, Jan. 11 (Yonhap) — South Korean stocks slipped Monday after choppy trading, roiled by foreign and institutional investors who sought to take profits before their stock options expire later this week. The Korean won fell against the U.S. dollar.

The benchmark Korea Composite Stock Price Index (KOSPI) fell 3.73 points, or 0.12 percent, to close at 3,148.45 points, breaking its two-day winning streak.

Trading volume was exceptionally high at about 1.7 billion shares worth some 44.1 trillion won (US$40.2 billion), with losers outnumbering gainers 712 to 170.

The stock market ran unusually volatile, with the KOSPI peaking at 3,266.23 points and bottoming at 3,096.19 points.

The KOSPI got off to a strong start on the back of stellar advances by Samsung Electronics and Hyundai Motor, as investors pinned rosy expectations on the top caps’ possible partnership with U.S. tech giants.

But the key stock index undid its gains, as institutions offloaded a net 3.7 trillion won and foreigners dumped a net 712 billion won. Retail investors bought a net 4.5 trillion won.

Analysts attributed the fall to a massive selling spree by institutions, which raked in local stocks for the year-end dividends last year and are apparently seeking to cash in profits ahead of the option expiration day on Thursday.

“From early December to the ex-dividend day, financial investment institutions bought some 4 trillion won worth of KOSPI 200 shares,” NH Investment & Securities analyst Noh Dong-kil said.

“Since the ex-dividend day, they have been cashing in these assets, which affected the KOSPI’s performance today,” he added.

Most large caps closed mixed in Seoul.

Samsung Electronics advanced 2.48 percent to record 91,000 won, following reports that it is competing with Taiwan Semiconductor Manufacturing Co. over a chip outsourcing deal offered by U.S. tech behemoth Intel Corp.

Hyundai Motor surged 8.74 percent to 267,500 won after logging a jaw-dropping two-digit hike the previous session, fueled by reports that South Korea’s largest carmaker may sign a deal on Apple’s autonomous electric cars.

Internet portal operator Naver moved down 0.96 percent to 309.000 won, while its rival Kakao jumped 4.38 percent to 435,000 won.

Leading chemical firm LG Chem edged down 0.1 percent to 998,000 won, and rechargeable battery maker Samsung SDI lost 1.22 percent to 730,000 won.

Pharmaceutical giant Samsung Biologics gained 1.08 percent to 846,000 won, and Celltrion rose 1.91 percent to 374,000 won.

The local currency closed at 1,097.3 won against the U.S. dollar, down 7.5 won from the previous session’s close.

Bond prices, which move inversely to yields, closed higher. The yield on three-year Treasurys lost 0.9 basis point to 0.969 percent, and the return on the benchmark five-year government bond fell 2.5 basis points to 1.301 percent.