UPDATE 1-Ireland to raise 4 bln euros in year's first bond sale, sources say

Ireland's debt agency is set to raise 4 billion euros in a new 10-year bond sale after being swamped with enough demand to raise over four times that amount, market sources told Reuters on Wednesday.

Investors put in 18.1 billion euros ($20.72 billion) of orders for the bonds, which will mature in May 2029, according to one banking source. That includes 2.5 billion euros of demand from the lead managers, the source said.

The deal is set to price at 27 basis points over mid-swaps, which translates to a yield of around 1.10 percent by Reuters calculations.

The deal is expected to price later on Wednesday. BNP Paribas, Bank of America Merrill Lynch, Citi, Davy and Societe Generale are managing the transaction.

Last week, banking sources told Reuters the Irish debt agency would look to complete the bond sale before the British parliament votes on UK Prime Minister Theresa May's Brexit agreement. The vote is set for next week.

Ireland is considered the euro zone country that would be most affected by a messy separation between the UK and the European Union. ($1 = 0.8735 euros) (Reporting by Graham Fahy; writing by Conor Humphries; eiting by Andrew Heavens, Larry King)