The benchmark Korea Composite Stock Price Index advanced 15.36 points, or 0.66 percent, to close at 2,359.08. Trade volume was low at 238 million shares worth 4.8 trillion won ($4.3 billion), with losers outnumbering gainers 416 to 396.
Institutions purchased a net 345.8 billion won worth of KOSPI shares, while foreign and individual investors offloaded a net 136.2 billion won and 232.9 billion won, respectively.
"Investor sentiment has improved on eased worries over geopolitical risks," said Lee Kyung-min, an analyst at Daeshin Securities, adding that not only the local bourse but also most Asian markets, including Japan, China and Taiwan, are enjoying upward momentum.
Most large caps closed mixed on the Seoul bourse, with tech and chemical shares leading the gain.
Top cap Samsung Electronics ended at 2,490,000 won, up 1.47 percent from the previous session's close. Smaller rival LG Electronics gained 0.73 percent to 83,100 won, and global chipmaker SK hynix jumped 1.65 percent to 73,800 won.
Chemical shares also closed higher. LG Chem, the country's top chemical firm, jumped 5.23 percent to 392,000 won, and No. 2 player Lotte Chemical was up 3.22 percent to 416,500 won
Meanwhile, auto stocks closed bearish, with leading automaker Hyundai Motor losing 0.37 percent to 135,000 won and its sister company, Kia Motors, shedding 0.62 percent to 31,800 won. Hyundai Mobis decreased 3.56 percent to 217,000 won.
The local currency closed at 1,131.9 won against the US dollar, down 4.4 won from Friday's close.
Bond prices, which move inversely to yields, ended mixed. The yield on three-year Treasurys shed 0.1 basis points at 1.757 percent and the return on the benchmark five-year government bonds added 0.6 basis point to 1.954 percent. (Yonhap)