In 2005-06 both MobiFone and Vinaphone claimed to have the biggest number of subscribers in Vietnam . However, after the ministry checked they discovered that the biggest operator in terms of subscribers was actually Viettel.

The 3G (third generation) segment has experienced the same problem. In 2010, mobile network operators reported they had a combined 3G subscription of 14 million while the ministry said the number stood at just seven million.

The mobile phone market is growing quickly. The number of subscribers skyrocketing in recent years from 19 million in 2006 to 98 million in 2009, and now 123.5 million so far in 2012.

In a letter sent to these operators, the ministry asked them to send monthly reports relating to their customer databases.

The letter follows the ministry's decision late last month to request more connections between the customer databases of mobile network operators and the ministry's own data centre.

The ministry says the move will help them supervise the number of mobile subscribers, phone tariffs and promotions, which will enable them to enforce prompt and efficient policies affecting the mobile market.

They have announced that the country's three biggest operators – Viettel, Vinaphone and MobiFone – will be required to report first and connect to the new system, with smaller operators following soon.