Suspected insurgents also shot dead two villagers and beheaded one of the victims and set off four of seven bombs meant to cripple power supplies in two districts.

Nopadol was leading a team to investigate one of the seven bomb sites, all of which were high power utility poles in the Muang and Tak Bai districts, when a booby-trapped bomb exploded after he stepped on it.

The colonel was evacuated by helicopter to Songkhla Nakarin Hospital in Hat Yai district.

The Office of Her Majesty the Queen's Principal Private Secretary expressed grave concern over Nopadol's condition and called the hospital to provide him with the best medical attention, said the hospital's director, Asst Professor Dr Sumate Pirawood.

The senior officer has been posted in the restive region for several years and has had several brushes with death, including a stand-off in April 2003 with a group of angry villagers holding two plainclothes police hostage because they thought they were bandits.

Police said four utility poles were severely damaged by the explosions. Three of the bombs were successfully defused. The incidents took place in Narthiwat's Tak Bai and Muang districts.

Maj-General Panya Thiensart, deputy commissioner of Ninth Police Region, said the booby-trap bomb that nearly killed Nopadol showed the insurgents had improved their methods of attack.

Normally, bombs are detonated remotely by mobile phone. But because the authorities usually cut off mobile phone signals, the insurgents have opted for booby-traps to trigger the devices.

A senior officer from the National Intelligence Agency (NIA), speaking on condition of anonymity, said the trigger mechanism greatly resembled the bombs used by Communist Party of Thailand insurgents a few decades ago, but authorities are still trying to determine if the bomb was home-made or factory built.

Niran Khongsaeng, 54, but not Damrong Thongrong, 58, were killed on their way to their longkong orchard in Tambon Cherngkiri in Narathiwat's Sri Sakorn district.

Police said they were confused as to why the culprits only beheaded Niran.

Niran is a resident of Yala's Tambon Talingchan, while Damrong is from Narathiwat's Tambon Sungai Padi. It was not clear if they were working as farm hands at the orchard or were the actual owners.

Police later spoke to a witness who was standing about 600 metres away from the crime scene. The witness said the victims were riding a tractor when four gunmen in black outfits and covered heads charged from the nearby wooded area and sprayed them with bullets. He watched one of the attackers behead Niran before fleeing into the woods.

Meanwhile, Thanongsak Phongpasert, director of the State Railways of Thailand in the South, said the service from Yala to Sungai Kolok will resume on April 23. The line was closed after gunmen opened fire on a train last week.

Police are looking for six suspects in connection with the train shooting.

The Nation

Narathiwat