Thai investigators have identified an "Arab looking" youth wearing a yellow T-shirt as the suspected bomber as he was seen placing a backpack at the Erawan shrine moments before the deadly blast.

The first images of the suspected bomber, wearing thick-rimmed glasses, have been released and the police have asked people to help them trace his identity.

Thai junta chief Prayut Chan-O-Cha told AFP that investigators believe that the suspected bomber is part of an "anti-government group based in Thailand's north-east" -- the stronghold of the Red Shirt movement. The group has been involved in several attacks in the past, but none has been of this intensity.

Thai news organisations, citing police sources, claim that the CCTV image shows a "Caucasian'' or ''Arab looking'' man placing the bomb under a bench before walking away while typing something on his mobile phone.

According to The Strait Times, speculations are rife that since Erawan shrine is popular with Chinese tourists, the attack could have been the work of Uighurs, a Turkic-speaking Muslim minority in the far west of China.

The Thailand government has set up a "war room" to hunt down the perpetrators of the bomb blast, which killed at least 20 people and injured dozens. At least eight tourists from China, Hong Kong, Indonesia, Malaysia and Singapore were killed in the attack.

Defence Minister Prawit Wongsuwan told Reuters that those responsible "intended to destroy the economy and tourism, because the incident occurred in the heart of the tourism district".

"It was a TNT bomb... the people who did it targeted foreigners and to damage tourism and the economy," he said.

CCTV Footage of the Blast Suspect [Video]