MADRID—Spain has raised (EURO)4.2 billion ($5.5 billion) in debt auctions at mostly lower interest rates, indicating improving investor confidence as the government ponders tapping a European financial facility that could ease its high borrowing costs.

The Treasury sold (EURO)1.12 billion in benchmark 10-year bonds Wednesday at an average interest rate of 5.29 percent, down from 5.46 percent in the last such auction Oct. 18.

It paid 3.39 percent, down from 3.62 percent, to sell (EURO)2.12 billion in three-year bonds.

The department sold (EURO)1 billion in bonds maturing in 2019, but at a yield of 4.67 percent, up from 4.54 percent.

Demand averaged twice the amount offered.

Recession-hit Spain says it must know all the conditions before requesting an international aid program for its public finances.