Trade surplus amounted to 4.6 billion U.S. dollars in March, up from a surplus of 3.8 billion dollars in the previous month, according to Korea Customs Service.
The trade balance stayed in black for the 98th consecutive month since February 2012.
Export, which takes up about half of the export-driven economy, shed 0.7 percent from a year earlier to 46.7 billion dollars in March, while import rose 0.3 percent to 42.1 billion dollars.
Semiconductor export slipped 3.0 percent last month, and shipments for oil products, ship and consumer electronics declined in double figures.
Outbound shipments for automobiles and car parts grew 7.2 percent and 0.9 percent respectively, with the export of telecommunication devices such as smartphone advancing 15.1 percent in the month.
Export to China, South Korea's biggest trading partner, retreated 6.2 percent in March from a year earlier, but those to the United States, the European Union (EU) and Japan gained 16.8 percent, 9.5 percent and 13.1 percent each.
For the first three months of this year, the trade surplus reached 8.7 billion dollars.
The export reduced 1.4 percent to 130.8 billion dollars in the three-month period compared with the same period of last year, while import dipped 1.4 percent to 122.1 billion dollars.
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