Southern insurgents set off bombs in Phatthalung and Satun provinces because security was now too tight in the three southernmost border provinces, Deputy Prime Minister Prawit Wongsuwon said on Monday.
Gen Prawit, also the defence minister, made the remark before leaving for Phatthalung and Satun with a senior security delegation including the deputy defence minister, the secretary-general of the National Security Council and the national police commissioner.
A series of bombs exploded in the two provinces on Saturday night and Sunday morning.
Gen Prawit said some suspects had been arrested in relation to the bombings, and they had links to the violence in the three southern border provinces of Narathiwat, Pattani and Yala.
"The culprits could do nothing in the three southern border provinces because authorities there are making full use of strategies and the forces. So they launched attacks outside those areas," he said.
Gen Prawit ruled out any political motive in the explosions in Phatthalung and Satun.
Panitan Wattanayagorn, security adviser to the deputy prime minister, said the arrested suspects were identified from surveillance camera footage and they were all wanted for insurgent activities in the South.
"More insurgents have moved to upper areas in the South, but still adhere to their old thoughts... They have safe houses to hold meetings and issue orders and local residents recommended bombing locations," he said.
Intelligence officials had warned of such an expansion in activity and recommended tight security until the general election. Besides, many young people had just arrived in Phatthalung for concerts, Mr Panitan said.
Gen Wallop Rugsanoh, secretary-general of the National Security Council, agreed with Gen Prawit about the spread of attacks by southern insurgents, but he did not rule out politics and vested interests as also being a possible motive.
The bombs in Phatthalung and Satun were aimed at causing panic, not taking lives, he added.