The Bank of Korea said the amount is the net of buying and selling of U.S. dollars by the central bank to intervene in the USD/KRW market during the six-months period.

"The currency market was relatively stable in the second half, hence the small figure," a BOK official said after the details were announced, when asked if the net amount used to stabilise the markets was small due to heavy intervention.

"We do intervene but we don't intervene to maintain or target a certain level except in cases where herd behaviour is seen and prices are skewed."

South Korea in May 2018 decided to disclose details of actions taken by currency authorities on a regular basis to improve the transparency of its "smoothing operations," a move that eased concerns about the country being labelled a currency manipulator by the United States.

Only the net amount used for smoothing operations is disclosed. The figures do not include the buying and selling of U.S. dollars separately.

FX intervention details for the first half of this year will be announced at the end of September. The BOK will start releasing the data on a quarterly basis from December, with figures from the September quarter.

The daily average volumes of USD/KRW transactions in the Korean interbank market amounted to $7.96 billion in 2018, data from the BOK shows.