Ireland's long-term government borrowing costs fell below 0.8% for the first time in nearly five weeks today after Moody's upgraded the country's credit rating. 

The lift by one notch to A3 from Baa1 means Ireland has won back an A category rating from all the major agencies, a move that some analysts said could broaden the international buyer base for Irish debt. 

Ireland's 10-year bond yield fell four basis points when markets re-opened to 0.78%, the lowest since 11 April.

Yields had already fallen some eight basis points on Friday in expectation of the upgrade.

"The upgrade by Moody's expands the range of potential buyers of Irish bonds. Some investors, particularly in Asia require a minimum A grade from all of the three big agencies," Cantor Fitzgerald strategist Ryan McGrath said. 

Moody's was the only agency to cut Irish debt to junk in 2011, months after the country entered a three-year international bailout. 

The agency, which kept a positive outlook on its new rating on Saturday, said in a statement that growth in the country has been better than expected in recent months. 

The Irish economy grew almost 8% last year, and is forecast to expand by close to 5% this year to remain the best performing economy in the European Union for a third successive year. 

That growth should cut the country's gross debt below 90% of gross domestic product by the end of the year, the country's Finance Department has predicted. 

Ratings agencies have been impressed by that sharp reversal from a peak of 125% during 2013. 

"The upgrade has highlighted the good news story about Ireland," Rabobank strategist Lyn Graham-Taylor said. "It is quite powerful how quickly their debt is coming down now." 

A vote on EU membership in one of Ireland's largest trading partners Britain next month also poses a significant risk.

In its statement, Moody's said that a UK exit from the European Union would have a negative impact on Ireland due to its close economic ties with Britain. 

"There may be some caution ahead given Ireland remains especially vulnerable to a Brexit vote," Societe Generale strategist Ciaran O'Hagan said.

Minister for Finance Michael Noonan said that Moody's decision showed the country is progressing in the correct direction.