Vietnam's five-year bonds fell the most in more than two weeks before an inflation report due this week.
Consumer prices climbed 23.02 percent in August from a year earlier, the fastest pace since November 2008, official data show. The General Statistics Office is due to publish data for September by Saturday.
The yield on five-year government notes rose two basis points, or 0.02 percentage point, to 12.47 percent, according to a daily fixing from banks compiled by Bloomberg. That's the biggest increase since Sept. 7.
"The trend is still unclear and investors are waiting" for the inflation report, said Nguyen Thanh Danh, a Ho Chi Minh City-based money-market dealer at Saigon Thuong Tin Commercial Joint-Stock Bank.
The dong strengthened 0.1 percent to 20,812 per dollar as of 3:20 p.m. in Hanoi, according to data compiled by Bloomberg. The central bank fixed the reference rate at 20,628 today, unchanged since Aug. 24, according to its website. The currency is allowed to trade up to 1 percent on either side of the rate.