The expansion was mainly due to a 4 percent quarter-on-quarter growth in government bonds to $51 billion, ADB said in the report released Wednesday.
The value of corporate bonds declined by 2.8 percent quarter-on-quarter to $5 billion, it added.
The SBV had in August ordered commercial banks to stop purchasing corporate bonds, a move aiming to minimize risks and tighten control over real estate sector borrowings.
Many local banks have issued bonds to increase capital since the beginning of the year. From January to August, bank bonds accounted for half of corporate bonds issued, according to top brokerage Saigon Securities Inc.
99.6 of bank bonds were bought, the highest ratio among all industries, it said.