Tran Ngoc Ha, head of the Criminal Police Department, said over 100 officers had been dispatched to arrest 31-year-old Bui Tuan Anh, a gang leader, along with over 20 other people on Sunday.
A search uncovered numerous weapons like guns, blades and ammunition, as well as betting tools.
Anh is a notorious gang leader, and his right arm is 34-year-old Tran The Vinh. Their underlings include around 50 others, operating mainly in bordering areas between Ho Chi Minh City, Binh Duong and Dong Nai.
"This group is responsible for multiple assaults, though their victims never dared report them to authorities as the group was too dangerous," said an investigator.
Anh confessed to having organized online soccer bets since 2019. At the height of the betting season, hundreds of billions of dong could flow through the group's accounts each night.
Investigators said the group had generated VND1.5 trillion through betting over its two years in operation.
Anh and other group members are under investigation for organizing gambling and illegally storing and using military weapons.
While Vietnam government has legalized sports betting and said it would allow people aged over 21 with a monthly income of at least VND10 million ($445) to gamble at designated casinos, online betting remains proscribed.