Market heavyweights retreated after US Republicans released a tax plan last week that would postpone promised corporate tax cuts in one year, prompting Wall Street to close lower Friday.

"KOSPI went down as traders took to the sidelines on rising uncertainties over the US tax reform bill," Jeong Dai, a researcher at Meritz Securities said. "Some investors cashed in gains from recent rallies on lack of momentum following the third-quarter earnings season."

Foreign investors and institutions sold a net 63.61 billion won and 226.71 billion worth of local stocks, while retail investors scooped up a net 257.83 billion won.

Tech shares traded mixed. Market kingpin Samsung Electronics inched down 0.04 percent to 2,819,000 won, and SK hynix, a major chipmaker, edged up 0.37 percent to 82,300 won.

Chemical shares trade bearish. SK Innovation, the nation's top refiner, dropped 3.79 percent to 203,000 won, and No. 3 S-Oil decreased 3.97 percent to 121,000 won.

Auto shares rose on hopes that improved ties with China would boost their sales in the major export destination. Leaders of the two nations agreed to improve relations during their meeting over the weekend on the sidelines of the Asia-Pacific Economic Cooperation Economic Leaders' Meeting in Vietnam.

Hyundai Motor, the No. 1 automaker, advanced 3.88 percent to 160,500 won, and its sister company Kia Motors gained 3.02 percent to 35,800 won. 

The local currency closed at 1,120.6 won against the US dollar, down 3.5 won from the previous session's close.

Bond prices, which move inversely to yields, fell. The yield on three-year Treasurys rose 2.3 basis points to 2.180 percent, and the return on benchmark five-year government bonds gained 3.5 basis points to 2.385 percent. (Yonhap)