The NBH said the reserves were boosted by proceeds from the sale of dollar-denominated bonds worth a total of $3.75 billion last month.

"The rise in reserves is due to the dollar issue of the debt agency AKK which was swapped to euros (EUR 2.6 bln), while the decline in some items are linked to debt servicing," the bank said in a reply to e-mailed questions.

Reserves have doubled since October 2008, when Hungary secured a loan package worth nearly 20 billion euros from the International Monetary Fund, the European Union and the World Bank.