The Fourth Region Army has ordered troops to hunt down attackers responsible for killing six rangers Thursday with a roadside bomb blast and ambush on their pickup patrol by gunmen in Chanae district of Narathiwat.
The bomb went off about 2pm as a patrol vehicle carrying a ranger team was approaching Ringae village in tambon Padungmart.
Troops in the South are forced to used pickups in combat operations, because armoured vehicles are kept at bases outside the region.
Gunmen hiding in the bushes on the side of the road then opened fire on the patrol, it was reported.
Four members of the patrol were confirmed killed at the scene. Two others, seriously wounded, died later said Pol Lt Sailom Roduppara, deputy investigation chief at Chanae police station.
The attackers poured petrol over the rangers' bodies and set them alight.
The dead soldiers were Sgt Pornchai Songkhor and ranger volunteers Veerawit Thamnam, Thara Kobket and Thanapong Thaweeprayoon.
Yutthayong Mungthirat and Manot Maitrisamphan sustained serious injuries.
The injured were being treated at Naradhiwasrajanagarindra Hospital.
Fourth Army Region commander Piyawat Nakawanich issued an urgent order for soldiers to look for the attackers.
The force is led by Col Wicha Sarikkapan, head of the 49th Ranger Battalion.
The search will be assisted by other security units.
Gen Piyawat is also director of the Fourth Region Internal Security Operations Command.
Authorities said the 10kg bomb in Thursday's attack was improvised, triggered remotely via a mobile phone.
According to security forces inspecting the attack scene, the six rangers were travelling in a pickup truck on their way back to their base from an official mission in downtown Muang district when they came across about 10 men dressed in uniforms similar to those worn by border patrol police.
The men were gathering on the roadside and shortly after the ranger team drove past them, the group set off the bomb and some of the attackers also emerged from the bushes and shot the rangers.
Before they fled, the attackers took six M16 rifles from the rangers.
The attackers scattered metal spikes on the road to prevent authorities from pursuing them.
Before Thursday's blast, 12 men were captured in separate raids on two villages in tambon Toh Deng of Sungai Padi district of Narathiwat.
The raids were conducted by more than 200 personnel in a combined force including rangers and police from nearby Yala province.
The men were detained as they were suspected to be members of groups connected to the southern unrest.
A security source said the detainees were split and brought for questioning at different places; six of them at the 46th Ranger Task Force, four at the 41st Ranger Task Force, and two at an undisclosed location.
Authorities seized some evidence including a cloth banner with a message criticising the junta government and slamming them for failing to understand local culture.
An investigation also found that most of the detainees are natives of the Sungai Padi district.