WASHINGTON — Interest rates on short-term Treasury bills rose in Monday’s auction, with rates on six-month bills climbing to their highest level since October 2008.

The Treasury Department auctioned $39 billion in three-month bills at a discount rate of 1.035 percent, up from 1.020 percent last week. Another $33 billion in six-month bills was auctioned at a discount rate of 1.140 percent, up from 1.115 percent last week.

The three-month rate was the highest since those bills averaged 1.040 percent on Aug. 7. The six-month rate was the highest since those bills averaged 1.400 percent on Oct. 27, 2008.