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 21 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," he said, adding the suspect was believed to be from an "anti-government group based in Thailand's northeast" -- the heartland of the kingdom's anti-coup Red Shirt movement.