South Korea's foreign currency reserves posted the first reduction in six months as the strong U.S. dollar lowered the conversion value of non-dollar assets, central bank data showed Wednesday.

Foreign reserves amounted to 409.17 billion U.S. dollars as of the end of February, down 0.48 billion dollars from a month earlier, according to the Bank of Korea (BOK).

It was the first decline in six months since August last year as the value of non-dollar assets fell on the back of the strong dollar.

The dollar index, which measures the dollar value versus six major peers, gained 0.6 percent last month.

The country's foreign currency reserves were composed of 371.22 billion dollars of securities, 27.1 billion dollars of deposits, 4.79 billion dollars of gold bullion, 3.27 billion dollars of special drawing rights (SDR) and 2.79 billion dollars of International Monetary Fund (IMF) positions.

South Korea was the world's ninth-largest holder of foreign reserves as of end-January, unchanged from the previous month.