Irish, Portuguese and Spanish bond yields hit fresh historic lows today and Portugal saw firm demand at an auction in the latest sign of strong investor interest for long-dated euro zone debt. 

In contrast to sharp yield falls across most European bond markets, Italian yields rose on concerns over tension within the ruling coalition. 

Portugal sold all €1.25 billion of the 10 and 15-year bonds it was offering today, with yields at the auction hitting record lows. 

Portuguese 10-year bond yields fell to a record low of 1.07% ahead of the auction and held close to that level afterwards. 

Spain's 10-year bond yield fell to 0.94% - its lowest in more than two years - and Irish long-dated bond yields dropped below 0.5% for the first time since December 2017. 

The National Treasury Management Agency said today it would sell a new 2050 bond via a syndicate of banks and analysts said the deal was likely to come before the end of the week. 

A weak economic backdrop and speculation that the European Central Bank will keep rates at record low levels for longer than anticipated has sparked a stellar rally in fixed income this year. 

Sluggish global growth and a dovish tone from central banks have also helped - New Zealand's central bank today cut interest rates for the first time in two and a half years. 

But with yields on higher-rated paper such as 10-year German debt below 0%, which essentially means investors are paying to hold those bonds, investors have moved into lower-rated markets to secure a yield. 

That makes a favourable backdrop for this week's euro zone bond sales, with focus now turning to Ireland. 

The NTMA's new 30-year bond comes just weeks after strong demand for a new 30-year Cypriot bond. 

"We've been getting fairly solid feedback on the long end - not just Ireland - for quite some time now," said a lead manager involved in the Irish deal. 

Most euro zone bond yields extended falls sparked by this week's downward revision to euro zone growth forecasts from the European Commission and renewed US/China trade tensions.

The European Commission also yesterday cut its growth prediction for Italy and said its public finances would deteriorate further, in an assessment that could reignite a dispute with Rome over its budget after the two sides reached an uneasy compromise in December.