The reserves of gold and gold receivables in the Eurosystem decreased by 7.1 billion last week, Dow Jones Newswires reports.
The Eurosystem, which is made up of the European Central Bank and the national central banks of the 13 countries that have the euro as their currency, now possesses gold reserves worth 172.756 billion.
Most of the decline (6.479 billion), was due to quarter-end adjustments, while around 631 million was due to transactions.
Net foreign currency declined by 1.6 billion to 144.3 billion over the week.
Last month it emerged that the Swiss National Bank (SNB) was to sell 250 tonnes of gold before the end of 2009, which will leave it with around 1,040 tonnes of the precious metal.
The sale, which is in line with limits agreed by the Eurosystem central banks and the SNB, will result in the bank's foreign exchange reserves increasing by a corresponding amount.