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The local currency was quoted at 1,024.1 versus the dollar at the end of onshore trade, down 0.4 percent from Friday's close at 1,020.
It was the biggest one-day percentage loss since May 14.
The Korea Composite Stock Price Index (KOSPI) closed up 0.4 percent at 2,002.00 points, bouncing back from a 0.9 percent fall on Friday to finish above the psychologically important 2,000-point threshold.
Offshore investors bought a net 209 billion won ($205 million) worth of KOSPI shares, extending their net buying streak to a 15th session.