After opening a tad higher, the index fluctuated between positive and negative territory throughout the session. Wall Street also finished mixed, with the Dow Jones industrial average edging up 0.04 percent and the Nasdaq composite falling 0.25 percent following strong gains in the previous session over the post-election relief.

"After the US central bank's meeting, the US dollar and Treasury yields rose, which caused a weakening of US shares," said Seo Sang-young, an expert at Kiwoom Securities.

On Thursday (US time), the Federal Reserve decided to stand pat on interest rates but maintained its previous stance that it would pull the trigger again next month in a move to continue to tighten monetary policy.

"Such a plan would add greater volatility to the market, though any serious downturn would be unlikely," he forecast.

Bio shares tumbled to drag down the index. Pharmaceutical giant Celltrion sank 3.77 percent to 229,500 won, and Samsung BioLogics skidded 4.29 percent to 368,000 won on suspicions over its alleged accounting fraud in 2015.

Chemicals also lost ground. LG Chem shed 2.24 percent to 327,500 won, and S-Oil plunged 4.17 percent to 115,000 won. LG Household & Health Care also slumped 4.8 percent to 1,110,000 won.

Tech shares overall traded higher, though top-cap ones had a mixed showing. Market bellwether Samsung Electronics added 0.57 percent to 44,300 won, while major chipmaker SK hynix remained unchanged at 72,900 won.

The South Korean currency closed at 1,128.3 won against the US dollar, down 11 won from Thursday's close.

Bond prices, which move inversely to yields, ended higher. The yield on three-year Treasurys was down 0.6 basis point to 1.960 percent, and the return on benchmark five-year government bonds rose 1.8 basis points to 2.069 percent. (Yonhap)