South Korea's foreign currency reserves maintained their record-breaking trend for five straight months in December, central bank data showed Friday.

Foreign reserves reached a fresh monthly high of 326.97 billion U.S. dollars as of the end of December, up from the previous record high of 326.09 billion dollars for November, according to the Bank of Korea (BOK).

The reserves topped the prior high for five months in a row last month, and stayed above the 300-billion-dollar level since April 2011 when it rose above the level for the first time in the country's history.

The 300-billion-dollar mark has been viewed as the psychologically-important level to protect the local financial market from potential foreign capital exodus from the country that may come from possible financial shocks.

The BOK attributed the December growth to a rise in investment returns. Conversion value of non-dollar assets showed mixed picture. The European single currency and the British pound appreciated 1.9 percent and 0.8 percent each against the U.S. dollar last month, but the Japanese yen and the Australian dollar depreciated 4.3 percent and 0.5 percent respectively.

The country's foreign reserves consisted of 299.86 billion dollars of securities, 7.04 billion dollars of deposits, 3.53 billion dollars of special drawing rights (SDR), 2.78 billion dollars of International Monetary Fund (IMF) positions and 3.76 billion dollars of gold bullion.

As of the end of November, South Korea was the world's seventh- largest holder of foreign reserves following China, Japan, Russia, Switzerland, China's Taiwan and Brazil.