The IGCP debt agency said the average yield on 18-month T-bills fell to 1.963 percent from 2.990 percent in the previous auction in late November.
It sold 1 billion euros of the 18-month issue.
One-year T-bills yielded 1.609 percent, down from 2.101 percent at the previous auction in October and the average yield on the three-month paper dropped to just 0.667 percent from 1.936 percent in November. The IGCP sold 300 million euros of 3-month bills and 1.2 billion euros of 12-month bills.
Demand outstripped the amount placed by 2.7 times on 18-month bills, 2.3 times on 12-month bills and 3.8 times on the shortest maturity, the IGCP said.
Portugal started issuing longer, 18-month T-bills last year and then swapped shorter-dated for longer bonds on Oct. 3 as part of its plan to stage a gradual return to debt markets. Its current 78-billion euro bailout programme covers the country's financing needs up until September 2013.
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