NARATHIWAT, Nov 25 (AFP) - Suspected Islamist insurgents have shot dead three Muslim civilians in Thailand's troubled south, the latest attacks in a nearly six-year separatist rebellion, police said Wednesday.

The bullet-riddled body of a 47-year-old man was found at his house in Narathiwat province early Wednesday. Police said he was probably attacked after returning home from a visit to a tea shop the previous night.

Separately, gunmen killed a 25-year-old Muslim in an ambush in neighbouring Yala province on Tuesday night. Another Muslim, aged 25, died in an attack the same night in Pattani province, said police.

A Buddhist man was shot three times in a drive-by attack in Narathiwat on Tuesday but survived with serious injuries, they added.

More than 4,000 people have been killed and thousands more wounded in Thailand's Muslim-majority provinces bordering Malaysia since the insurgency erupted in January 2004.

Tensions have simmered in the region, formerly an autonomous Malay Muslim sultanate, since it was annexed by predominantly Buddhist Thailand in 1902.