South Korea's terms of trade improved last month as import costs fell at a steeper pace than export prices amid lower commodity prices, central bank data showed Tuesday.

The net terms-of-trade index for goods, a gauge of trade terms, rose 5.4 percent in June from a year earlier after gaining 6.1 percent in the prior month, according to the Bank of Korea (BOK). The index is calculated by dividing export prices by import prices.

The continued rise came amid faster fall in import costs than export prices caused by a decline in prices for crude oil and steel products.

The import price index tumbled 5.5 percent last month, while the export price index slid 0.4 percent.

The income terms-of-trade index, which measures how much can be imported with money earned via exports, rose 4 percent in June from a year ago after jumping 16.1 percent in the previous month.

The slower growth was attributable to a fall in export volume, which declined 1.4 percent on-year in June on weak demand for oil products and primary steel products.