VPBank, ACB and Agribank has been raising at least VND1.5 trillion ($65.9 million) a month since April.

June was a peak period with an average of three successful issuances every day by a host of companies, including lenders such as BIDV, TPBank and SHB and real estate developers like Phat Dat, Hung Thinh and BIM.

Stock brokerages and aviation, construction and energy firms also raised up to VND1 trillion each during the month.

In the first seven months of the year, there were 376 issuances worth a total of VND235 trillion, according to the Vietnam Bond Market Association.

There were three international issuances that raised a total of $1 billion.

Banks topped the list, accounting for 40 percent of the total value. Most of them offered coupon rates of 3-4.2 percent.

Most real estate developers offered over 8 percent.

The boom had been forecast at the beginning of the year.

Analysts at financial data provider FiinGroup foresaw a rising need for funds as banks began to tighten lending.

Besides, the pandemic dried up short-term cash flows and caused companies with good long-term prospects to restructure their debts, the company said in a note.

"Amid the high demand for mid-term and long-term funds and a fluctuating stock market, corporate bonds were a strategic choice for both listed and unlisted businesses."

Economist Nguyen Tri Hieu said many retail investors also invest in bonds because of their high interest rates.

The Ministry of Finance on Sep. 1 ordered relevant agencies to increase oversight of the corporate bond market since many small and newly established companies are making issuances.

This is the second time in a year that the ministry has voiced concern about corporate bonds.