CCTV video footage has been released showing the moment the suspect linked to the Bangkok bombing in which at least 22 people have been killed slips off his backpack in the area just minutes before the explosion occurs.

The video footage, posted to Facebook by Thai news agency Thairath, shows an unidentified man in a yellow T-shirt carrying a backpack walk through the crowds at the Ratchaprasong road junction in the centre of the city. He proceeds to slip off his backpack on a bench by the Hindu Erawan Shrine before departing.

A timestamp on the CCTV video marks the incident as taking place at 6.40pm local time, just 20 minutes before the bomb exploded. And following the attack, 123 people are believed to be in hospital recovering from injuries.

The video comes after Thai police released their first images of the same suspect. "That man was carrying a backpack and walked past the scene at the time of the incident. But we need to look at the before and after CCTV footage to see if there is a link," Thai national police chief Somyot Poompanmoung said.

Poompanmoung added that the bomb was made with a pipe wrapped in cloth and weighed 3kg. Nobody has claimed credit for the attack.

On 18 August, an explosive was tossed at Bangkok's central Sathorn pier, a main tourist boat depot, but it bounced into the water causing no injuries or damage.