South Korea's trade surplus stood at 2.2 billion U.S. dollars in May due to brisk exports of oil products and wireless communication devices, the nation's customs office said Wednesday.

Trade surplus reached 2.2 billion dollars in May, down from 4 billion dollars a year earlier, the Korea Customs Service (KCS) said in a statement. The May reading marked the 16th straight month of surplus since February 2010.

Exports grew 22.4 percent on-year to 47.6 billion dollars last month, while imports expanded 30.1 percent on-year to 45.4 billion dollars, according to the KCS.

The May exports were lower than a record high of 48.6 billion dollars tallied for April, but it was attributable to reduced working days last month, the KCS said.

Strong exports of oil-related products and mobile communication gadgets led the May export growth. Outbound shipments of petroleum products surged 82.1 percent on-year last month, with exports of wireless communication devices and ships jumped 47.6 percent and 23.5 percent respectively.

Shipments bound for the United States marked a fresh record high of 5.2 billion dollars in May, up 24.7 percent from a year earlier. Exports to China and Japan remained robust by growing 19. 8 percent and 36.8 percent on-year respectively.

Meanwhile, imports jumped mostly due to higher costs of raw materials, with imports of crude oil and natural gas surged 37.5 percent and 26.1 percent on-year each last month.