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The local currency stood at 1,116.5 against the dollar at 0025 GMT, down half a percent compared to Friday's domestic close at 1,111.1.
Trade is expected to be thin on Monday as some Asian markets, including Australia and Hong Kong, along with Europe are still closed for Easter holidays.
South Korean economic data announced early on Monday also weighed on the won as inflation remained low and exports grew slower than expected as Asia's fourth-largest economy struggles to recover.
The benchmark Korea Composite Stock Price Index was down 0.2 percent.