Tuesday's sale is the first stage of the EU's ambitious plan to increase its debt pile 15-fold in less than a decade to fund its two coronavirus support programmes for member states, which brings it closer to debt mutualisation than ever before.
In time the EU, until now a tiny borrower on a par with Slovakia, will become one of Europe's biggest borrowers.
Tuesday's sale was closely watched to see how successful the bloc might be at ramping up its borrowing at such speed and how much it would cost.
With the sale the EU has already funded over half of the 30 billion euros of debt it expects to sell this year.
The shorter bond, which will raise 10 billion euros, attracted over 145 billion euros of final demand on its own, also a record high for a single European bond tranche, lead managers said.
"This is sending a strong signal that they can upsize their issuance without much difficulties," said Antoine Bouvet, senior rates strategist at ING.
The bonds attracted investors as they offer a yield higher than safe-haven German bonds, which have very similar credit ratings, and also higher than French bonds, which are rated lower than the EU.
The EU is rated Triple A - the top credit rating - by two of the three main ratings agencies.
"It's really on that valuation basis that they appear attractive to us," said Gareth Hill, a fund manager at Royal Asset Management who put in orders for both EU bonds on Tuesday.
Another factor boosting demand was the European Central Bank, which currently underbuying bonds from supranational institutions, should hoover up a good deal of the debt in the secondary market.
The social bond format, a type of sustainable debt to fund spending beneficial to society, also helped attract demand, bankers said. Up to 100 billion euros of issuance to back SURE by the end of 2021 will triple the outstanding social bond universe, according to ING.
The 10-year bond was due to price for a yield of around -0.25% and the 20-year at around 0.12%, according to Reuters calculations based on pricing from lead managers.
The 20-year bond, which will raise 7 billion euros, received over 88 billion euros of demand, lead managers said.
After SURE the EU will start financing its larger programme, an 800 billion euro recovery fund next year, although it has yet to be ratified by member states divided over tying disbursements to the rule of law.
($1 = 0.8464 euros)
(Reporting by Yoruk Bahceli; Editing by Susan Fenton) ((Yoruk.Bahceli@thomsonreuters.com; +44 20 7542 7571; Reuters Messaging: email@example.com))