Photo: VCG

At least 15 people were gunned down in an ambush by suspected Muslim militants in Thailand's violence-wracked south, an army spokesman said Wednesday, one of the bloodiest days in the 15-year insurgency.

Thailand's three southernmost provinces have been in the grip of a conflict that has killed more than 7,000 people, as Malay-Muslim militants fight for more autonomy from the Thai state.

The region is heavily controlled by the police and the military, with residents and rights groups accusing them of heavy-handed tactics.

Villagers trained and armed by security forces are also enlisted to monitor remote villages, though they are rarely targeted by the rebels.

This changed late Tuesday when militants struck two checkpoints in Yala province manned by civilian defense volunteers, opening fire on them as a group of villagers stopped to talk, southern army spokesman Pramote Prom-in told AFP.

In the largest death toll in years, "12 were killed at the scene, two more [died] at the hospital, and one died this morning," said Pramote, adding that five others were injured.

The attackers took M-16 rifles and shotguns from the checkpoints, he said. "These acts were by militants."

Nails were also scattered on the roads in an apparent effort to slow the security forces, the army said in a separate statement.

A bomb squad was dispatched on Wednesday morning to investigate and detonate an explosive device suspected to have been left by fleeing attackers about three kilometers from one checkpoint.