The benchmark Korea Composite Stock Price Index shed 9.81 points, or 0.45 percent, to finish at 2,165.79. Trading volume was slim at 278.9 million shares worth 4.6 trillion won ($4.22 billion), with losers outnumbering gainers 623 to 219.
The index opened lower, tracking Wall Street losses, and fluctuated throughout the session. It once rose to positive terrain but ended up extending its losing run for a fifth straight session.
Institutions offloaded a net 113.6 billion won worth of local shares, while retailers picked up shares worth 111.5 billion won.
Foreigners also picked up a net 280 million won worth of local shares, ending their selling binge for the past five sessions.
"While investors are awaiting progress in a trade deal between the US and China, concerns over the global economic slowdown seem to spoil their appetite for risk," said Kim Yu-kyum, an expert at Cape Investment & Securities, citing the recent low-volume sessions.
In its latest report, the Organization for Economic Cooperation and Development forecast 3.3 percent growth worldwide this year, down from 3.6 percent last year, while warning of a slowdown in most of the world's largest economies.
"Expectations for China's economic stimulus measures also appear to cause investors to shift their eyes from the Seoul market to China," he added.
Bio and chemical shares lost ground in the Seoul bourse, though tech blue chips rose on investors' bargain hunting.
Major biopharmaceutical firm Celltrion fell 1.9 percent to 207,000 won, and Samsung BioLogics decreased 0.79 percent to 375,000 won.
Leading chemical firm LG Chem skidded 1.88 percent to 366,000 won, and top steelmaker POSCO dropped 1.76 percent to 250,500 won.
But market bellwether Samsung Electronics spiked 1.02 percent to 44,450 won, with chip giant SK hynix remaining unchanged at 68,100 won. Top carmaker Hyundai Motor also rose 0.8 percent to 125,500 won.
The local currency was trading at 1,129.00 won against the US dollar, down 0.2 won from the previous session. (Yonhap)