WASHINGTON (AP) — Interest rates on short-term Treasury bills rose in Monday's auction with rates on six-month bills rising to the highest level since March 2011.

The Treasury Department auctioned $32 billion in three-month bills at a discount rate of 0.105 percent, up from 0.100 percent last week. Another $28 billion in six-month bills was auctioned at a discount rate of 0.150 percent, up from 0.145 percent last week.

The three-month rate was the highest since these bills averaged 0.110 percent on Sept. 24. The six-month rate was the highest since these bills averaged 0.170 percent on March 28, 2011.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,997.35, while a six-month bill sold for $9,992.42. That would equal an annualized rate of 0.106 percent for the three-month bills and 0.152 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, edged up to 0.18 percent last week from 0.17 percent the previous week.