Security has been intensified in the far South ahead of Sunday's ninth anniversary of the Krue Se mosque incident in Pattani.
Officials are also worried about the possibility of reprisal attacks after three suspected insurgents were killed by authorities on Friday.
Troops and police are on full alert at Pattani's Krue Se mosque for Sunday's anniversary of the killing of 32 militants (inset) inside the mosque. (File photos)
Security surveillance operations have been stepped up in Pattani since Friday night in anticipation of a possible strike by insurgents to mark the anniversary of the Krue Se massacre.
Combined forces of soldiers, police, local administration officials and defence volunteers set up roadblocks and searched high-risk areas throughout the province.
Authorities had received intelligence that an attack was being planned in which two pickup trucks and two cars laden with bombs would be detonated in Pattani, a security source said.
There were also concerns of revenge attacks after three suspected insurgents were killed in a raid on their forest hideout in Yala's Bannang Sata district on Friday.
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The men had been implicated in the roadside bomb attack that killed Yala deputy governor Issara Thongthawat and assistant governor Chaovalit Chairuek on April 5.
However, DNA tests on the suspects' bodies showed they had not been involved in that attack.
The three dead men were identified as Boonya Daleng, Budimun Mayi and Abdul Tolae Saha.
Yala police commander Pol Maj Gen Peera Boonliang said Boonya was believed to be among 50 armed militants who attacked a marine base in Narathiwat's Bacho district on Feb 13.
He said Budimun was wanted for allegedly killing villagers in a religious ceremony in Yala's Bannang Sata district, while Abdul Tolae faced charges of killing two paratroopers in the same district.
The police commander said he believed Abdulloh Tapotoh, a leading rebel responsible for the killing of the deputy governor and the assistant governor, was with the three insurgents during the forest raid, but managed to escape.
Former Internal Security Operations Command chief Panlop Pinmanee, said instigating large-scale attacks during important events was highly symbolic for the insurgents and an act of self-aggrandisement.
He said the insurgents were mostly young people who received militant training abroad.
Gen Panlop is held responsible by many for the Krue Se massacre, as he ordered the armed raid on the mosque to flush out suspected militants on April 28, 2004.
All 32 suspects inside the mosque were killed in the attack.
Also in Pattani Saturday, one ranger was killed in a gun attack and two others wounded in separate violent incidents.
In the first incident, Muhammai Saifu Abdultolep, a ranger, was shot and seriously wounded in a drive-by shooting in tambon Manang Dalam in Sai Buri district while going to work. He died later in hospital.
In the other incident, a bomb was detonated while a team of rangers was on foot patrol near Moo 3 village in tambon Paseyawo in Sai Buri district.
A clash between the rangers and the militants ensued after the explosion.
Two rangers - Thirasak Sudari, 25, and Sithichai Thammachart, 22 - were wounded and sent to Sai Buri Hospital.
National police chief Adul Saengsingkaew said the first batch of 1,982 new policemen would be deployed in the three southernmost provinces on Wednesday.