Bangkok, Aug 19 (IANS): Thai police on Wednesday offered a reward of 1 million baht ($28,100) for any information leading to the capture of the prime suspect in Monday's Bangkok explosion in which at least 20 people were killed and more than 100 others injured.

The police released a sketch of the suspected perpetrator who was seen on a surveillance camera at the scene, reported Xinhua.

Camera footage showed that a foreign-looking, young man, who was wearing a yellow T-shirt and glasses, left a backpack purportedly with some dynamite inside at Erawan Shrine, a popular tourist destination in Bangkok, shortly before the explosion.

The shrine reopened on Wednesday amid heightened security, but far fewer tourists visited it than before.

Thai Prime Minister Prayut Chan-o-cha urged the "amateur" culprit to surrender to the police, warning he could otherwise be killed.

"The bombing suspect could probably be killed if he does not surrender. His life is being fatally jeopardised by those who had hired him and might be looking to silence him," Prayut said.

Meanwhile, police chief Somyot Poompanmoung said the bombing was carried out by "a network".