The country's top prosecutors have charged eight defendants for using gambling websites to commit fraud.
Seven Ho Chi Minh City residents including their alleged ring leader Ly Hue Quyen and one from Hanoi had been operating the pages www.colonyinvest.net and www.callyinvest.com between April and November 2007, the indictment said.
The group stands accused of "committing frauds to appropriate others' property."
Quyen pocketed VND32.3 billion from the scam, prosecutors say.
Investigators found that the group said their websites were of big international companies doing business in casinos, hotels and information technology.
The eight defendants allegedly cheated thousands of people, from all over the country, out of a total of VND58 billion (US$3 million) by claiming to offer huge returns on their investments.
The indictment alleges that the investors were tricked into buying "virtual points" on the website at one dollar a piece. Quyen and his accomplices supposedly attracted investors by promising that each "virtual point" would pay 2.5-3 percent interest every day.
Prosecutors also claim that the investors were promised a commission for inviting more people to the websites.
The People's Court in the Mekong Delta's Dong Thap Province was the first to hear of the case. The lower court transferred the matter to the Ministry of Public Security for further investigation.