(VOVworld) – Thailand’s police chief Somyot Poompanmuang has said that at least ten people were suspected of involvement in Monday’s bomb attack on the Erawan shrine in Bangkok which killed 20 people.

Police issued a sketch of the main suspect in the Bangkok bombing (Photo: AFP/Reuters)

The police chief told reporters on Thursday that the attack must have been prepared by a number of people including those who looked out on the streets, who prepared the bomb, those at the site, and those who planned the escape route.

Police have issued an arrest warrant for an "unidentified foreign man" in a yellow shirt seen on closed circuit video footage and have said investigators believe two other men seen in the footage were accomplices.

Earlier, police said they believed at least three people, including a foreigner, were involved in the attack at the famous city shrine.