This will be done over the next three months in an attempt to rein in the number of subscribers, many of whom have more than one phone so that they can take advantage of special rate deals.

However, a senior policeman, Major General Nguyen Cong Son, said many criminals took advantage of mobile phones for illegal activities, including sending hundreds of messages "scamming" for reply fees, harassing people and even using them to detonate mines.

The subscriber data sent to police is from the latest update of the three main mobile networks – Viettel, MobiFone and VinaPhone.

According to the information ministry, much of the personal information recorded for prepaid mobile phones is suspect.

Earlier, cross-checks in Ha Noi and Da Nang cities found that as many as 25 per cent of the now compulsory registrations were incorrect.

Despite being told to re-register with correct information, it was difficult to persuade customers to comply.

Many subscribers buy SIM-cards when special deals are available – and they switch from phone to phone to take advantage of each offer.

The information ministry has told the networks to cancel any existing contracts if the customers with incorrect information fail to re-register.

However, cross-checking, has been a slow progress. For instance, it took one year to check on data in Ha Noi and Da Nang.

That's why police have been asked to co-ordinate more closely with the information ministry, said Major General Son.

He said police would cross-check personal information of prepaid subscribers with their identity cards.

Source: VNS