South Korea's central bank increased the portion of U.S. dollar-denominated assets in its foreign exchange reserves by nearly 4 percentage points last year from a year prior on expectations of a strengthening greenback, a report showed Tuesday.

Dollar holdings accounted for 62.5 percent of the Bank of Korea (BOK)'s foreign assets last year, up from 58.3 percent in the previous year, according to the central bank's annual policy report.

"(The 2014 reading) results from an expansion in the portion of U.S. dollar-denominated assets on forecasts that the U.S. dollar will strengthen in tandem with a favorable economic recovery," the central bank said in the report.

The 2014 result marks a recovery to the 60-percent range after the figure backtracked to the 50-percent rage for the past two years. The reading has mostly remained at the 60-percent level since the BOK began disclosing the data in 2007.

With the rise in greenback assets, the portion of assets denominated in other currencies fell to 37.5 percent from 41.7 percent. The BOK does not disclose the details of assets in other currencies.

As of the end of 2014, 37.1 percent of the BOK's foreign assets were invested in government bonds, up 0.3 percentage point from the previous year, while 22.5 percent was parked in state agency bonds, up 0.5 percentage point from a year ago.

The portion of corporate bonds gained 1.6 percentage points to 17.5 percent while that of asset-backed securities fell 1.8 percentage points to 13 percent, according to the report.

Korea's foreign reserves stood at US$363.6 billion as of the end of last year, with foreign currency-denominated assets accounting for roughly 97 percent of the total.

The BOK entrusts 15.2 percent of the assets to global asset managers and the country's sovereign wealth fund Korea Investment Corp. (Yonhap)