MADRID, Oct 18 (Reuters) - Spain's funding costs fell at auction on Thursday, when the Treasury sold 4.6 billion euros ($6.3 billion) of bonds, after Moody's affirmed the country's investment-grade credit rating and as markets expected Madrid to ask for aid soon.
Spain had been aiming to sell between 3.5 billion and 4.5 billion euros of the three bonds.
The benchmark 10-year bond, due Jan. 31, 2022, sold at an average yield of 5.458 percent, down from its previous primary auction Sept. 20, when it fetched a yield of 5.666 percent.
The Treasury sold 1.5 billion euros of the bond and received 1.9 times as many orders. That compared to 2.8 times when it last auctioned.
The bond maturing July 30, 2015, sold 1.6 billion euros at an average yield of 3.227 percent and with a bid-to-cover ratio of 2.6. The same paper last sold Sept. 6 at a yield of 3.676 percent and a bid-to-cover of 1.8.
The bond due Oct. 31, 2016, sold 1.5 billion euros with a yield of 3.977 percent, compared to 4.603 percent when it last sold, Sept. 6.
The bond was 2.6 times subscribed, seeing greater demand than when it last auctioned, when it was 1.9 times subscribed.