The won strengthened 4.1 won from the previous session to close daytime trading at 1,382.4 per dollar, compared with Friday's 1,386.5.
The currency briefly strengthened to 1,376.5 during the session and extended its advance for a seventh straight trading day, the longest such streak since December 2013.
Month-end dollar selling by exporters and offshore bets on further won appreciation coincided with the currency's gains. A steep equity selloff and heavy foreign stock outflows accompanied a partial pullback late in the session.
The KOSPI tumbled 3.12 percent to 6,696.96 as Samsung Electronics plunged after its shareholder-return plan fell short of elevated market expectations. Foreign investors sold about 3.68 trillion won ($2.66 billion) of shares.
Korean government bonds also strengthened. The three-year yield fell 1.3 basis points to 3.836 percent, the five-year declined 4.3 basis points to 4.068 percent and the 10-year dropped 4.1 basis points to 4.335 percent.
U.S. Treasury yields and oil prices were higher early in the session, while foreign investors bought three- and 10-year bond futures as domestic bonds turned higher.
An auction of a new five-year government bond produced accepted yields ranging from 4.095 percent to 4.135 percent, a split that coincided with a temporary pause in the rally.
Bonds regained momentum as the equity selloff deepened in the afternoon, with longer maturities outperforming and the 10-year yield falling 2.8 basis points more than the policy-sensitive three-year yield.
The move produced a bull-flattening of the yield curve ahead of the Bank of Korea's rate-setting meeting on Thursday.
Markets are divided over whether the BOK will follow its July 25-basis-point increase with another hike.
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