The alleged mastermind behind the Bangkok shrine blast arrived in Bangladesh the day before the August 17 incident and left for China two weeks later, police said yesterday.

A senior police official made the disclosure after receiving a notice sent by the Thailand police through the Interpol for help to locate Abu Dustar Abdulrahman alias Izan, a Chinese national.

"We received a message from the Thai police around 4:00pm. We verified the message and found that the man flew to Dhaka on a Biman flight from Bangkok on August 16. He landed at the airport in Dhaka around 3:30pm local time," Assistant Inspector General (Media) Nazrul Islam told The Daily Star.

Izan then left Dhaka for Beijing on August 30 on a Jet Airways flight, he said, adding that they had already informed the Thai authorities of the development.

Asked where Izan had been living or which places he had visited during his stay in Bangladesh, Nazrul said, "This is part of our ongoing intelligence activities and I have restrictions on disclosing the information right now."

At least 20 people were killed and over a hundred injured in the attack outside a Hindu shrine at Erawan in central Bangkok.

On Wednesday, Thai daily The Nation reported that the country's police through the Interpol had requested cooperation from Dhaka after their investigations indicated the "mastermind" behind the blast had fled to Dhaka.

Meanwhile, Bangladesh Ambassador to Thailand Saida Muna Tasneem told The Daily Star last night that the government would extend all-out cooperation to Thailand to pinpoint Izan's movements during his two-week stay in Bangladesh.