Two people were killed and at least 36 wounded in a car bomb explosion on Friday afternoon in downtown Betong, a town in Yala that has been relatively trouble-free during the decade-long southern insurgency.
The Betong Holiday Hill hotel and several cars were damaged by the blast.
The explosives were hidden in a Toyota Vigo pickup truck parked in front of the Betong Holiday Hill hotel on Bhakdi Damrong Road in tambon Betong.
The explosion at 4.40pm damaged the hotel building, cars and motorycles in the area and sparked a fire in a house and a convenience store.
The area was locked down while security officials and rescue workers helped the wounded.
Yala governor Dejrat Simsiri was quoted as saying that the casualities were high because a fruit fair was being held in the area.
The dead were identified as Miss Pennapa Toonhor, 23, and Mr Decho Dareeyoh. Most of those injured people were Betong residents.
The suspected bomb truck caught on tape
Authorities reported later that the bomb was planted in the truck bearing the plate number Bor Khor 8594 Betong. The explosion also caused a blackout and local people said it was the first violent explosion in downtown Betong in years.
The attack was launched when local security guards were changing their shift, said Col Banpote Pulpian, a spokesman for the Internal Security Operations Command (Isoc).
Sources said that security authorities were looking for a Yala-Don Yang-Hat Yai passenger van with the licence plate number 10-1010 that had been parked to reserve a location for the truck bearing the explosives. The van arrived at about 2.50pm and the pickup truck later replaced it.
The driver of the truck boarded the van and it left.
A source said that authorities had not expected Betong would be attacked so violently, although authorities had warned of a possible car bomb attack late in the Ramadan month of Muslim fasting, the source said.
Col Pramote Phrom-in, a spokesman for the southern office of the Isoc, said that army chief Prayuth Chan-ocha had told 4th Army chief Lt Gen Walit Rojanaphakdi to bring the situation under control quickly and intensify security measures to prevent repeated attacks. Authorities were also told to step up security measures to prevent car bombings in the three southern border provinces as well as Hat Yai district of Songkhla.
In Narathiwat, a roadside bomb killed one paramilitary ranger and injured three of his friends in Sukhirin district at 3.30pm on Friday.
Security authorities believe a small cooking gas cylinder stuffed with explosives was detonated with a communication radio when four paramilitary rangers were riding two motorcycles back from an evening teacher protection trip and heading for their base, the 11th Paramilitary Ranger Regiment.
The explosive cylinder believed to weigh about 25 kilogrammes was placed on the ground near a power pole on a local road in Moo 2 village of Kia sub-district. The impact tore the pole into two pieces.
The dead man was indentified as ranger Phakdi sae Oon, 26, and the injured are private Thianchai Panla, 25, ranger Khomsan Phuakngam, 23, and ranger Chatchai Khamphu, 25.
