The Spanish treasury raised four billion euros ($5.3 billion) in a surprise issue of 10-year bonds on Wednesday, more than the two to three billion it had originally intended, Spanish media reported.

The syndicated bond issue has received strong demand of over 8.0 billion euros, several media reports said, with the bonds placed at an average rate of return for investors of 5.4503 percent.

The banks that handled the bond sale are Barclays, BBVA, Deutsche Bank, Goldman Sachs, Santander and Societe Generale.

The surprise bond issue came amid falling yields on government bonds from highly indebted nations on the eurozone periphery.

With the country set to slump into recession, the government has taken advantage of the situation to place greater amounts of debt than initially planned for the beginning of the year.

Spain has already completed a quarter of its gross bond issue plan for this year, which totals 86 billion euros.

-- Dow Jones Newswires contributed to this report --