The issue, which had an original target of 1.25 billion euros, was subscribed more than 3.5 times over, the debt management agency said.

A month previously the debt agency had raised 390 million euros at a 4.64 percent rate of return for investors.

"The total bids reached 4,485 million euros and the amount finally accepted was 1,625 million euros," the PDMA agency said.

Moody's on Monday slashed Greece's credit rating by three notches from Ba1 to B1 and warned it could be downgraded further given the risks to the country's stabilisation efforts.

Moody's said the downgrade reflected its concerns over Greek efforts to balance its strained public finances, despite efforts made following a bailout it received last year from the European Union and International Monetary Fund to avoid default.

The Greek government said the decision was "completely unjustified" as it came only days before a crucial summit of euro-zone leaders to discuss plans for a permanent European debt rescue system.