Nguyen Huu Loc, 41, a Quang Nam resident, has been identified as the leader of the ring.
As of Monday, provincial police have arrested more than 20 suspects involved in the gambling and betting ring led by Loc.
The arrests came after police found that Loc organized for others to bet on matches of the ongoing European Football Championship and the Copa America.
On June 30, authorities summoned Loc and more than 20 people for questioning.
After extracting data from May 23, authorities accused the group of organizing online gambling involving more than VND50 billion.
The case is currently under further investigation.
In Vietnam, most forms of gambling, including sports betting, are illegal, with some exceptions such as state-run lotteries.