Spain comfortably sold just shy of 4 billion euros (3.20 billion pounds) of three bonds on Thursday with yields falling on two of them on confidence the country will soon seek European aid to cut its debt costs.

The Treasury sold 1.3 billion euros of bonds maturing in October 2014, 2 billion euros of a bond maturing in October 2015, and 710 million euros of a five year bond. Together they were at the top end of the Treasury's 3 billion to 4 billion euro target.

Spain remains at the centre of investors concerns in the euro crisis, fearful its deficit cutting targets will be impossible to meet as the country slides into a deep recession.

Investors expect Spain to eventually request a bailout, and that helped yields to fall on two of the bonds on Thursday even if holding at high levels.

The yield on the 2014 bond was 3.282 percent after 5.204 percent when it was last sold on July 19. The 2017 bond had an average yield of 4.766 percent, compared with 6.459 percent the last time it was sold on the same date in July.

The 2015 bond had a yield of 3.956 percent, compared with 3.845 percent when it was last sold on September 20.

All three saw demand increase from when they were last sold, with strong interest in the five-year bond.

(Reporting by Madrid bureau; Writing by Nigel Davies; Editing by Julien Toyer)