They said Tuesday that the nine, who remain unidentified, were arrested last week in HCMC, the central province of Khanh Hoa, the southern province of Long An and the northern province of Bac Ninh.

Preliminary investigations have traced the gambling ring to Cambodian casinos. A group of Vietnamese who went to work in Cambodian casinos in 2015 cooperated with Cambodian gambling ring leaders to set up the Winxxx website for Vietnamese gamblers.

Winxxx provides several gambling, betting services through online casinos for soccer, basketball and tennis matches.

Gamblers are given Vietnamese bank accounts to transfer money to the ring's organizers in the country.

The ring is being investigated further.

Vietnam legalized sports betting in 2017 and allowing, on a pilot basis, people aged over 21 with a monthly income of at least VND10 million ($432) to play in a casino on the southern Phu Quoc Island. However, all other forms of gambling remain illegal.