The government is tightening up security measures in the wake of Saturday's car park grenade attack, after suspects told police more strikes are planned for Sunday, said the National Security Council Tuesday.
Police say they are preparing for trouble after a key suspect in the Criminal Court car park bombing said more violence was planned, supposedly at 100 locations this Sunday.
Yutthana Yenpinyo, a 34-year-old Yasothon resident, and Mahahin Khunthong, also 34, from Pathum Thani, were arrested shortly after the grenades were launched at the court car park on Ratchadaphisek Road on Saturday evening.
The pair, who police say were also behind a Feb 1 blast near Siam BTS, allegedly told officers that more incidents designed to provoke chaos are planned, but did not provide details.
In response, police are boosting security, including increasing patrols, particularly at places considered prone to such attacks, said NSC secretary-general Anusit Khunakorn.
Mr Anusit said there were no confirmed reports the bombing was masterminded by any group or person overseas.
However, Mr Mahahin allegedly told police he and Mr Yutthana were hired by an Australia-based human rights activist named "Dear".
He also claimed Mr Dear threatened to harm his family and blackmail him by disclosing their conversations on the Line mobile application to the public.
Mr Mahahin also allegedly admitted being a key member of Seri Chon, an underground group which opposes the military-installed government.
When asked if Seri Chon and the Seri Thai group, led by former deputy leader of the Pheu Thai Party Charupong Ruangsuwan, were connected, Mr Anusit hesitated to draw a link. However, he said the NSC is closely monitoring their movements.
Prime Minister Prayut Chan-o-cha said investigations have exposed the suspects' ties to groups involved in the 2010 violence.
The security intelligence unit is monitoring underground movements, said Gen Prayut, adding that once there is sufficient evidence to prove who is behind the attacks, they will be prosecuted. He insisted the government is not persecuting any particular political camp.
City police chief Pol Lt Gen Sriwara Rangsiphramnakul said an additional suspect, Wichai Yusuk, has now been detained in connection with the grenade attack, bringing the total number of suspects held by the military to five. Nine people are still wanted by police.