Interest rates on short-term Treasury bills rose in Monday's auction to the highest levels since August.

The Treasury Department auctioned $29 billion in three-month bills at a discount rate of 0.04 percent, up from 0.025 percent last week. Another $27 billion in six-month bills was auctioned at a discount rate of 0.07 percent, up from 0.06 percent last week.

The three-month rate was the highest since three-month bills averaged 0.045 percent on Aug. 8. The six-month rate was the highest since these bills averaged 0.08 percent on Aug. 16.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,998.99 while a six-month bill sold for $9,996.46. That would equal an annualized rate of 0.041 percent for the three-month bills and 0.071 percent for the six-month bills.

Separately, the Federal Reserve said Monday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, was unchanged at 0.11 percent last week, the same as the previous week.