Thailand's junta chief on Tuesday said authorities are hunting a "suspect" seen on CCTV footage near the scene of a bombing that claimed at least 20 lives in Bangkok and wounded scores more.
"Today there is a suspect who appeared on CCTV but it's not clear... we are looking for this guy," Prime Minister Prayut Chan-O-Cha said.
He also said he believed Facebook messages apparently warning of an imminent danger to Bangkok ahead of the bomb came from an "anti-government group" based in Thailand's northeast -- the heartland of the kingdom's anti-coup Red Shirt movement.
"We are looking for them now, some of them are in Isaan (northeastern Thailand)."
A second explosion hit the capital on Tuesday, with no injuries reported.
Since 2006 Bangkok has witnessed repeated rounds of deadly violence, flanked by two coups which have seen the military claim the streets.
But foreigners have rarely been caught up in the bloodshed.
The most recent coup in 2014 toppled the elected government of Yingluck Shinawatra after months of disruptive and occasionally deadly street protests.
The Red Shirts are a grassroot network filled with rural and urban poor, particularly from the country's northeastern regions, that are loyal to Yingluck and her also ousted prime minister brother Thaksin Shinawatra.
Authorities have blamed them for a string of small explosions in Bangkok earlier this year, a charge their leadership has strongly denied.
They were also initially blamed by authorities for a car bomb on the reort island of Koh Samui earlier this year, but police were later forced to back-track.
While the Red Shirts more militant members have been known to launch attacks on security forces or government buildings, they have not launched a mass casualty bombing that targets foreigners.
Thailand's Islamist insurgents are also not known to target foreigners and have also largely kept their violent attacks to the three Muslim-majority provinces in the country's south neighbouring Malaysia.