Vietlott said they had protected the winner's identity as requested after many people raised doubts about the company's credibility when it gave the prize to a masked man on October 18.

On October 16, 32-year-old Nguyen Thi Anh Dao from Tra Vinh was revealed as the lottery winner of over VND92bn (USD4.14m) of Mega 6/45 by Vietnam Computerised Lottery One Member Limited Liability Company, Vietlott.

Dao said her father named Thai would go to HCM City to receive the prize on October 18. Her house was surrounded on October 19 after Dao said she had plans to donate some money to charity organisations and hundreds of gifts to poor people.

However, images of the awards ceremony appeared on October 18 showing a masked man accepting the prize. Security was tightened for the ceremony and reporters were not allowed to attend. The man was only revealed as a middle-aged man named Thai from Tra Vinh Province.

A masked man named Thai received the prize on October 19

According to Vietlott, representative of the Ministry of Security, the company provides surveillance software, Thai and his family attended the ceremony. Vietlott said it already transferred the prize after tax, VND82bn, to Thai.

On the pictures provided by Vietlott, Thai wore a mask while accepting the prize and this has raised doubt from the public about the company's transparency, especially when many people had suspected that Vietlott might not be able to gather such huge amount of money in five days.

However, Vietlott said the winner requested to remain anonymous in accordance with Circular 75 on the confidentiality of prize-winners.

"By the request, we could only announce the first name, sex and the province," Vietlott's representative said. "Thai also only wore the mask when the pictures were taken. The ceremony lasted for one hour and attended by representatives of state agencies."

After news that the VND92bn prize found its winner, many people are flocking to buy tickets with the hope that they would win the next grand prize that is worth VND12bn. Vietlott said their ticket sales were increasing each day.

After the Jackpot prize was announced, their lottery ticket sales on the next Monday increased by 5%. Revenue in neighbouring Can Tho city to Tra Vinh, increased by 30% and the revenue in HCM City, where the winning ticket sold, increased by 230%.