Police said on Tuesday that the investigation was launched as part of a nationwide campaign targeting illegal weapons and other crimes.
Investigators discovered multiple social media accounts posting videos and images of firearms with capabilities similar to military weapons while offering guns, ammunition and components for sale to buyers in HCM City and several southern provinces.
Police identified Nguyen Ngoc Son, 33, from Tan Son Nhi Ward, as the alleged ringleader. According to investigators, Son assembled firearms resembling military weapons, tested them, recorded demonstration videos and uploaded them online to attract buyers.
The weapons and ammunition were concealed in parcels and transported on interprovincial buses, while payments were made through bank accounts registered in other people's names to conceal the transactions.
Between May 30 and June 6, police, working with authorities in several localities, arrested more than 30 suspects in HCM City and the provinces of Tay Ninh, Dong Thap and Vinh Long.
Officers seized 27 firearms, including 14 military-grade weapons, nine partially assembled guns, nearly 100 gun parts under manufacture or modification, around 1,000 rounds of ammunition, and machinery and equipment used to make firearms.
Based on the evidence collected, investigators charged 30 suspects with illegally manufacturing, trading and possessing military weapons. Additional charges relating to drug trafficking and organising illegal drug use were also filed.
The investigation later uncovered seven more suspects allegedly involved in drug trafficking and organising illegal drug use, while inquiries are continuing to trace the source of the weapons and identify other people linked to the network.
Authorities said the case showed how criminal groups were using social media to manufacture and trade military-grade weapons, and prevented a large number of illegal firearms from entering circulation.