Treasurys accelerated earlier gains on Thursday following strong demand for a sale of 30-year bonds.
The Treasury Department auctioned $16 billion in 30-year bonds at a high yield of 3.224 percent, the lowest since May 2013. The bid-to-cover ratio, an indicator of demand, was 2.60, above a recent average of 2.40.
In the "when-issued" market, bonds were expected to sell at a yield at 3.2480 percent.
Indirect bidders, which include major central banks, were awarded 45.9 percent, while direct bidders took 44 percent of the pile.
Benchmark 10-year Treasurys were up 6/32 in price with a yield of 2.41 down from 2.42 percent before the announcement, while, 30-year bonds surged 22/32 in price, bringing the yield down to 3.21 percent from 3.24 percent earlier.