More than 80 percent of mobile phone users in Indonesia, Malaysia, Thailand and Philippines buy pre-paid cell phone cards without having to give a name and address.

Several Asian governments are imposing stricter control on the sale of pre-paid phone cards. They hope that registering users of mobile phones will be one way of helping to curb terrorism and crime.

In the developing countries of Asia, most mobile phone users are anonymous. More than 80 percent of mobile phone users in Indonesia, Malaysia, Thailand and the Philippines buy pre-paid phone cards without having to give a name and address. The cards are popular because they are cheap, easy to buy and because phone users can control what they spend in phone calls.

But a number of Asian governments think that the anonymous ownership and use of mobile phones has become a security concern, and they want to register users of pre-paid cards.

Nathan Burley is an analyst with a telecommunications and software consulting company Ovum, in Melbourne. He says security services want to remove a tool from the hands of terrorists, who have used pre-paid phone services to detonate bombs, for example, in Spain and Thailand.

"There has also been a push to combat general criminal activity, which has been the case in Malaysia, and there is also a push in that direction in Japan," said Nathan Burley.

The anonymity of pre-paid cards has enabled criminals to develop a range of telephone scams to separate gullible people from their money, and has made it difficult for police to chase them.

Thailand started to register users of pre-paid phone cards in May. The initiative was triggered by a series of bomb blasts in Thailand's predominately Muslim southern provinces, where security forces face an insurgency that has killed at least 1,000 people. The bombs had mainly been detonated by mobile phones.

In Singapore, stricter controls for pre-paid phone cards will start in November, as part of the country's efforts to tighten security against possible terror attacks. Mobile phone users with pre-paid SIM cards in Malaysia will also have to register with their service providers by the end of this year.

Taiwan introduced strict regulations on pre-paid cards last year, mainly to crack down on phone scams. Customers now need identification to buy phone cards, and can only buy one per person. As a result, pre-paid sales went down and many operators lost subscribers.

Telecom consultant Nathan Burley says increased regulation of the sale of pre-paid cards could also be bad news for consumers.

"Any registration will reduce competition," he said. "There will be increased management costs, you have to log extra details, if their sales channels are limited because they can't provide corrected registered places - it's going to be a bad thing for the consumer."

Registering their customers will be a huge task for service providers. In Malaysia alone, 14 million users of pre-paid phone cards need to be registered by the end of this year.