By Amy Sawitta Lefevre

BANGKOK (Reuters) - Suspected Muslim rebels killed three military rangers in a roadside bomb attack in southern Thailand on Thursday before security officials sat down to talks with rebel groups aimed at ending the bloody insurgency.

Two rangers died at the scene of the explosion on a road in Narathiwat province while a third died in hospital, police said. Five were wounded by shrapnel.

The blast came as Paradorn Pattanathabutr, secretary-general of the Thai National Security Council, and rebel leaders gathered in Kuala Lumpur for talks brokered by the Malaysian government.

Thai media reported that nine insurgent groups were due to join the talks, including the Barisan Revolusi Nasional (BRN). Hassan Taib, head of its liaison office in Malaysia, signed the agreement with Paradorn to pursue the talks on February 28.

"The BRN are the main group instigating violence in the south and they are who we should be talking to, but they will need time to reduce the number of attacks in the south," Paradorn told reporters in Kuala Lumpur.

"Our key goal today is to reduce violence."

Thai security forces say the BRN is the main insurgent organization behind the attacks in the south but have acknowledged that other armed groups operate there.

Some analysts are pessimistic about the peace talks and say the BRN has little control over the fighters.

The military, which has 60,000 troops stationed in the south, has been lukewarm about the talks and some generals have dismissed the insurgency as more criminal than political.

At least 27 people have died in the three southern provinces of Pattani, Yala and Narathiwat since February 28. In all, more than 5,300 have died since January 2004 when the insurgency resurfaced after simmering for decades.

The three violence-plagued provinces were once part of an independent Malay Muslim sultanate until annexed by predominantly Buddhist Thailand in 1909.

It remains unclear what the rebel groups want, although some say they are seeking autonomy or self-rule.

That was flatly ruled out by the Thai government on Thursday.

"One thing we will never do is break up Thailand. There will be no independent state of Pattani or special administrative zone," Deputy Prime Minister Chalerm Yoobumrung told reporters.

(Additional reporting by Pracha Hariraksapitak in Bangkok and Angie Teo in Kuala Lumpur; Editing by Alan Raybould)