Foreign tourists crowd a currency exchange booth in central Seoul's Myeong-dong tourist district, Friday. Yonhap

The Korean won has surged to become the best performing major currency against the dollar this month, buoyed by exporter dollar sales and the Bank of Korea's first policy rate increase in three and a half years, the data showed Sunday.

The won gained 6.24 percent against the dollar from July 1 through Friday, the biggest advance among 20 major currencies tracked by Yonhap Infomax. The Australian dollar and Russian ruble were the next best performers, each rising 0.9 percent.

The rally stands out against a backdrop of broad dollar strength. The U.S. dollar index has remained above 101, as geopolitical tensions between the United States and Iran sustained demand for safe-haven assets.

The Korean currency strengthened to 1,458.5 won per dollar in trading that ended at 6 a.m. Saturday, with the exchange rate falling 15.7 won from the previous session.