The 3-billion-euro top-up of the 2.80% March 2067 bond drew bids of more than 17 billion euros, with a final yield of 2.877%.

"The response was very good," Davide Iacovoni said in an interview.

He said 84% of the total demand came from abroad.  Some 35% were German buyers, 22% were from Britain and the rest were mainly in continental Europe. Outside Europe, U.S investors bought around 8%, while just 2% went to Asia.

In terms of account types, pensions funds and insurers bought some 32%, fund managers took up 31%, while 21% went to banks and 13% to hedge funds. Central banks and other official institutions accounted for about 3%, Iacovoni said.