More than 640 people have been killed, some in bomb blasts, since a separatist insurgency erupted in Thailand's three Muslim-majority southern provinces in January last year.

``All the mobile phone operators had agreed in principle to register SIM card buyers' information based on 13 digits on their identification card so that we can trace them,'' said Khanawat Wasinsungvorn, the vice-minister for Information and Communication Technology, in Bangkok Tuesday.

Most of more than 120 bombs detonated over the past 15 months - including a blast this month at the airport in Hat Yai, southern Thailand's business hub and a tourist gate into to the region - were triggered by mobiles, Matichon reported, citing figures from its own tally and a security analyst.

Prime Minister Thaksin Shinawatra said he is confident the new measure will help reduce bomb attacks and be welcomed by the public without the government having to introduce any new law forcing telecom operators to comply.

``Absolutely, I'm confident that if the measure is in place, it will ease bombing attacks significantly,'' Thaksin said.

But, he added, militants may switch to buying SIM cards from other countries. ``If they cannot use locally bought SIM cards, then they will buy mobile phones from overseas, so we also have to find measures to control the roaming system.''

Thaksin said there is no problem for operators to register the more than 20 million prepaid users because the system is computerized.

AGENCE FRANCE-PRESSE