Japan's foreign-exchange reserves at the end of May were up a record $43.65 billion from a month earlier to $543.09 billion, hitting an all-time high for the sixth straight month, the Finance Ministry said Friday.

The rise was mainly due to currency market interventions -- to the tune of approximately 4 trillion yen -- in the reporting month, a ministry official told reporters.

Japan intervened heavily in May to stem a rapid rise in the yen. The amount of money used for the operations was a monthly record.

The strengthening of the euro against the dollar also contributed to the increase in foreign-exchange reserves by pushing up the value of Japan's euro-denominated assets in dollar terms, according to the official.

The increase in the value of U.S. bonds and an increase in interest income from various investments were also viewed as factors, according to the official.

The previous all-time high for the nation's foreign-exchange reserves was $499.44 billion at the end of April.

The previous record for a monthly increase was set in April 2000, when it rose by about $33 billion.

Japan remained the largest holder of foreign reserves of any country or territory for the 42nd straight month, according to the latest comparable data.

Foreign-exchange reserves consist of securities and deposits denominated in foreign currencies plus International Monetary Fund reserve positions, IMF special drawing rights and gold.

Japan had $441.83 billion in foreign securities in May, up from $409.30 billion in April, and $81.96 billion in foreign currency deposits, up from $71.69 billion.

Of the deposits, $7.50 billion was at foreign central banks and the Swiss-based Bank for International Settlements, $40.33 billion at Japanese banks and $34.13 billion at foreign banks.

Japan also had $8.89 billion in gold, up from $8.29 billion in April.

It had $7.81 billion in IMF reserve positions and $2.59 billion in special drawing rights.