Do Anh Tuan, deputy head of the Department of Cybersecurity under the Ministry of Public Security, said Wednesday: "[The bookmakers] create hundreds of websites and set up servers outside Vietnam. Especially noteworthy is the fact that gambling and the organization of gambling have been carried out recently through online games that simulate actual gambling."

Gambling has been dealt with as a "social evil" for long by Vietnamese authorities. The government showed signs of changing attitudes in 2017 when it legalized sports betting and said it would allow Vietnamese citizens aged over 21 with a monthly income of at least VND10 million ($445) to gamble at designated casinos. Online betting, however, remains illegal.

Tuan said those running the online gambling rings utilize intermediary servers and foreign domains and routinely change server addresses to evade detection, he said.

Thousands of people gamble millions of dollars on these sites every day, he said.

Besides, Vietnam is facing "complex, dangerous" cyber-attacks on its national information systems with over 4,000 websites and information portals with Vietnamese domains attacked by hackers in 2018, he said.

Fake news and contents that promote violence, prostitution and child sexual abuse are also circulating in its cyberspace, he said, pointing out the Internet could also be used by criminals to buy weapons and explosives.

The government has been making efforts to tighten cybersecurity. The new Cybersecurity Law that came into effect at the beginning of this year bans Internet users from organizing, encouraging or training other people for anti-government purposes.

The law also requires foreign businesses to open representative offices in Vietnam and store their Vietnamese users' data in Vietnamese territory.

Businesses have to provide users’ data to the Ministry of Public Security if it asks in writing to facilitate investigation of any infringement of the new law.

Last November the communications ministry said it wanted half of social media users on domestic social networks by 2020 and plans to prevent "toxic" information on Facebook and Google.