South Korea's terms of trade fell for the third consecutive month in June due to a rise in prices of imported goods, central bank data showed Wednesday.

The nation's net terms-of-trade index for goods -- a gauge of trade terms -- declined 3.7 percent last month from a year earlier, according to preliminary data from the Bank of Korea (BOK).

The figure is calculated by dividing the index for export prices by that for import prices. It shows the amount of imports a country can buy for each unit of exports. The base year is 2015, with a benchmark index of 100.

Last month, the index for customs-cleared export prices went up 15.7 percent from the previous year, marking the eighth straight month of increase.

The index for import prices rose 11 percent from a year earlier, according to the data. (Yonhap)