The reserves, the world's second largest after China's, reached an all-time high for the third straight month.

Japan's foreign exchange reserves consist mainly of securities and deposits denominated in foreign currencies, gold, and reserve positions and special drawing rights at the International Monetary Fund.

The ministry on Monday also released data on asset management yields in the foreign exchange fund special account for fiscal 2009. They stood at 3.69 percent, down from the previous fiscal year's 4.32 percent, which were calculated in terms of the yen.

In addition to the yen's rise against the U.S. dollar, the fall stemmed from a drop in U.S. interest rates in the period, the ministry said.

Other annual data released included foreign currency securities by period of maturity.

For the year ended March 31, 2009, 23.3 percent of securities in foreign currencies had maturity terms of one year or shorter, while 51.0 percent had terms of between over one year and five years and the rest more than five years.

The ministry, which started to release data on maturity terms the previous year, said government bonds accounted for 68.6 percent of the securities.