A war room has been set up as authorities tighten up security in Songkhla after recent attacks in the province.
The Songkhla provincial police have also alerted security units in Chana, Sabayoi, Thepha and Nathawi districts to be on the lookout for possible violence.
About 4am on Sunday, a bomb exploded in Chana district, damaging six motorcycles and the shopfront of a motorcycle repair shop.
Police believed an incendiary bomb went off in front of the motorcycle repair shop in tambon Ban Na.
Administrative officials and defence volunteers, led by assistant district chief Chalermchai Wisuthichanon, rushed to the scene upon being informed of the incident.
While the team was about 500 metres from the shop, a roadside bomb exploded, slightly damaging the armoured vehicle they were travelling in. No one was hurt by the explosion.
Explosive ordnance disposal police arrived shortly afterwards, along with from officers from the 9th Forensic Centre.
A 5-kg improvised explosive device was found about 1 metre under the road, a source said.
A team of investigators led by Pol Col Anurut Im-arb, deputy Songkhla police chief, has been assembled to look into the case and track the suspects.
Initially, officers believed the explosions were set up to lure officers, who were the real target of the attack, a source said.
Another source said there were likely to be two teams of suspects who worked in pairs -- one team was responsible for attacking the motorcycle shop, while the other team attacked the officers.
Investigators believed the insurgents were the same group who shot a couple, owners of a furniture shop in Thepa district on Sept 2, the source said.
The group was led by Mayakoh Lateh, he added.
Meanwhile in Narathiwat, two village defence volunteers were killed and two others wounded in a gun attack by a group of gunmen in tambon Chang Phuak of Chanae district on Saturday afternoon.
Pol Lt Adipong Promnu, a Chanae police investigator, said that according to witnesses, about 5.20pm approximately five armed men emerged from roadside bushes and opened fire at house No 281 and a sentry box near a building used as the village's learning centre.
It was initially believed that separatists were behind the attack.
Four village defence volunteers, two men and two women, were hit by gunshots. One of them, Mrs Uab Uthai, the house owner, was killed instantly in front of the house. Three others -- Siboonruang Uthai, Wanpen Uthai and Boonlert Chotchoi -- were injured.
Siboonruang died shortly afterwards. Two others were admitted to Sungai Kolok Hospital.