The Internal Security Operations Command (Isoc) Region 4 says it has identified suspects behind the deadly bombing at a noodle shop in Pattani's Muang district on Monday night.
The blast, which occurred about 7pm in the municipality night market, killed a 60-year-old woman and wounded 21 others, including two who were seriously injured.
One of them, a Mathayom 6 student at the Prince of Songkla Demonstration School, identified as Narisara Makchuchit, was working at the shop where the bomb exploded.
The girl was taken to Songklanagarind Hospital in Hat Yai of Songkhla province after the attack. She has had one of her legs amputated and an eye removed, Naewna Online reported.
The other seriously injured victim is a seven-year-old boy named Prompiriya Promnukul.
He had to undergo a major surgery last night due to his injuries and is still receiving treatment at the intensive care unit of Pattani Hospital.
Nine other people were still in hospital under treatment, while the rest have been released.
The blast, which was caused by a home-made bomb in a steel box detonated remotely by a mobile phone, also caused extensive damage to stores nearby.
The incident took place a day before the 12th anniversary of the so-called Tak Bai incident in which 85 Muslim men died after being arrested and packed into trucks by army and paramilitary forces sent to Narathiwat's Tak Bai district to break up an anti-government protest.
Isoc Region 4 spokesman Pramote Phrom-in condemned the bomb attack, calling it "inhuman". He added his agency wishes to extend condolences to the families of those who were killed or injured.
Col Pramote also said 4th Army Region commander Lt Gen Piyawat Nakwanich was keen to ensure the injured victims receive the best possible care.
The colonel also said the perpetrators could be seen clearly in CCTV footage, adding the same people had previously carried out an attack at Pattani Central Mosque.
He did not give further details.
Wanchai Shinpha, the 57-year-old owner of the noodle shop where the blast occured, said this was the second bomb attack since he started the business more than 30 years ago.
The first attack took place in 2007, but Monday's blast was more damaging, he said.
He said he was slightly injured in the blast while his wife and two children were also hurt, adding his employees sustained severe injuries.
"Although I feel scared, I will not give up. I will not leave," said Mr Wanchai.
Lt Gen Piyawat, Pattani governor Veeranan Pengchan and other officials yesterday morning inspected the scene of the blast, which has been cordoned off for collection of evidence.
Lt Gen Piyawat spoke to owners of the affected shops to give them moral support. Accompanied by Mr Veeranan, he also visited the injured victims at the hospital yesterday.
Lt Gen Piyawat instructed officials to quickly track down the perpetrators and provide assistance to the victims.
He also provided financial assistance to 11 people who were receiving treatment at Pattani Hospital yesterday including the two who sustained life-threatening injuries.
Prime Minister Prayut Chan-o-cha said the attack had been carried out by insurgents who wanted to show muscle as the southern peace talks are ongoing.
He said the government and intelligence units will take all necessary measures to bring the situation under control.
"We do not want to see [the insurgents] become more bold. This could bring about a climate of fear," said Gen Prayut. "Officials are ready to make the sacrifice. We do not want any civilians to get hurt, not a single one," the prime minister said.
Condemning the attack, Women's Agenda for Peace (PAW) and 23 civil organisations urged all parties to resume the southern peace talks quickly and draw up safety zones.
