Spain has raised 4.9 billion euros ($6.4 billion) at slightly lower interest rates in a debt auction that saw strong demand as the country considers whether to request international help to manage its finances.

The Treasury sold 3.4 billion euros in 12-month bills at an average interest rate of 2.82 percent, down from 2.84 percent in the last such auction Sept. 18.

It sold 1.5 billion euros in 18-month bills at a rate of 3.02 percent, down from 3.04 percent.

The sale Tuesday was the first since credit rating agency Standard & Poor's last week cut its rating on Spain's debt by two notches to BBB-minus, just a step above junk status.

Demand was 2.78 times the amount offered in the shorter bills and 3.6 times for the longer bills.