Police suspect the bomb attacks in Satun and Phatthalung last week were carried out by the same group responsible for last year's bombing of Songkhla's iconic mermaid statue.
Deputy national police chief Srivara Ransibrahmanakul said Wednesday that an analysis of security camera footage from both incidents showed the same type of equipment and vehicle were used to carry out the bombings.
Authorities believe the 17 coordinated bombings -- 11 in Phatthalung's Muang and Pak Phayun districts, and six in Satun's Muang district -- involved some students of several privately-run Islamic schools, who were assisted by local residents sympathetic to their cause.
However, the attackers involved in the Phatthalung and Satun bombings are not local residents, Pol Gen Srivara said, adding between two and six perpetrators came from the three restive southernmost provinces nearby.
Intelligence authorities say insurgent groups are shifting their activities to other provinces to make it difficult for officers to plan security measures.
The deputy chief said that authorities had received intelligence about an impending attack in Satun and Phatthalung about one week before the incidents took place -- however, he declined to elaborate further.
Security personnel in the deep South will continue to beef up security as the government will hold advance voting on Sunday for the general election that will be held on March 24.
Soldiers will join police officers to lookout for irregularities at polling booths and along the roads to voting stations, Pol Gen Srivara said.
Separately, army chief Gen Apirat Kongsompong said Wednesday that in cases of emergencies during the election period, helicopters will be on standby to transport the ballot boxes.
