The yield on the benchmark 10-year government bonds ended up 2 basis points, while lead September futures on three-year treasury bonds ended down 0.07 points at 105.55.
The Bank of Korea (BoK) on Wednesday bought 700 billion won ($624.51 million) worth of local government bonds through a competitive auction, mostly in five-year and 10-year debt. The debt will be used for the central bank's open market operations.
The BOK's purchases had little effect on markets, however, as investors had priced in the move a day earlier.