Interest rates on short-term Treasury securities rose in this week's auction to the highest level in two weeks.

The Treasury Department sold $9.6 billion in three-month bills at an average discount rate of 5.94 percent, up from 5.86 percent last week. Another $9.6 billion was sold in six-month bills at an average discount rate of 5.91 percent, up from 5.85 percent last week.The three-month bill rate was the highest since they sold for 5.97 percent on Feb. 4. The six-month bill rate was the lowest since they averaged 5.94 percent on the same day.

The new discount rates understate the actual return to investors - 6.11 percent for three-month bills with a $10,000 bill selling for $9,849.90 and 6.18 percent for a six-month bill selling for $9,701.20.