BEIJING - China's foreign exchange reserves rose to $3.82 trillion at the end of 2013, $509.7 billion more than a year earlier, a central bank official said on Wednesday.

Growth of the nation's foreign exchange reserves was back on the fast track in 2013 with a quarterly increase of around $160 billion for both the third and fourth quarter.

The net increase in 2013 also sharply overrode the $130 billion net increase in 2012.

The data came after the nation's customs authority said last week that the trade surplus widened to $259.75 billion in 2013, an increase of 12.8 percent from a year earlier.

Meanwhile, foreign direct investment (FDI) in China kept expanding. Government data showed the country's FDI inflow stood at $105.51 billion for the Jan-Nov period, up 5.48 percent year on year.

The nation's foreign exchange reserves totaled around $100 billion in 1996. It took only a decade for China to surpass Japan to become the largest holder of foreign exchange reserves in 2006, when reserves topped $1 trillion.

Currently, the nation's foreign exchange reserves are almost three times that of Japan.

However, with the growing reserves, concerns have arisen on their management and value.

Zhao Qingming, a professor at the Beijing-based University of International Business and Economics, said that the nation's vast foreign exchange reserves are mainly used to invest in treasury bonds and financial bonds, which carry low interest rates. For instance, the ten-year yield of US Treasury bonds is only 2.8 percent.