Last Thursday suspected Islamic insurgents disguised as students bombed 22 commercial banks in a coordinated action.

The explosions left a retired army officer dead and 24 others injured.

Police said militants carried bombs hidden in school folders, books and bags and left them on bank writing counters. The attacks led to all banks in the province closing. At least five schools decided to shut.

August 31 was the anniversary of the founding of the Bersatu separatist movement and Malaysian National Day.

Police report the suspect admitted during questioning he had been told to rendezvous on Rattakij Road in Betong district.

He was promised Bt2,000 by a village elder.

At 10am on August 31 he kept the appointment and was handed a book by the elder. It contained Bt2,000 hidden in the flyleaf.

Police reported the suspect told them the book concealed a bomb.

Upon receipt of the cash he allegedly agreed to plant the device in a bank.

Betong Police Superintendent Col Songkiat Wathakul said the man allegedly revealed that suspect Witthaya Tohmean was involved in the bomb plot. Witthaya was arrested on Saturday in possession of gunpowder, an electrical-circuit manual, a 60-centimetre knife and a note reading "be careful with the mission".

Police reported Witthaya gave them names of others allegedly involved.

Police claimed at least 50 people took part in the coordinated explosions, and they were not all locals. Police were scouring hotels and the border for other bombers.

Police now had four people in custody and hoped to secure more arrest warrants soon.

Meanwhile, commercial banks in Yala will reopen today. They said they were confident of their safety after meeting with Army Region 4 commanders on Friday.

"We will reopen [today] after damage has been repaired. We understand customers have financial errands to finish, particularly at the beginning of the month," said Sub-Lt Nopporn Thammasart, the manager of the Yala branch of the Bank of Ayudhya.

He asked customers to be patient with tightened security at banks and cooperate with personal searches. It was for everyone's safety.

Banks would ask head offices to supply metal detectors similar to those employed at airports, said acting Yala Banker Association chairperson Narissara Kulchotirat.

In spite of the cost the machines were necessary for the security and safety of customers and bank staff, said Narissara.

The association would propose banks consider increasing risk allowances paid to staff in the three southernmost provinces.

Narissara, who is also the manager of the Yala branch of UOB Bank, said bank officers currently received between Bt3,000 and Bt5,000 a month in danger money.

Separately, local academics, religious leaders and peace advocates supported Army Commander Sonthi Boonyaratglin and his call for talks with separatist leaders.

Former National Reconciliation Commission member Ahmad Somboonbualuang said it was a good idea to negotiate. It now depended on the government to agree.

More than 1,400 people have been killed in South troubles since January 2004. Almost-daily attacks include drive-by shootings, arsons and bombings. The targets were often government officials and teachers.