A man arrested over a deadly bombing at a Bangkok shrine confessed to handing a backpack filled with explosives to another man who then left it at the blast site and is still on the run.

Meanwhile security sources named the alleged mastermind of the attack as Abudureheman Abudusataer, a Chinese national from the Xinjiang region.

The developments came as Thai police brought Yusufu Mierili, one of the two suspects currently in custody, to the train station for a public re-enactment of the alleged handover. The 25-year-old was arrested earlier this month as he was attempting to flee the country into Cambodia.

Police said that during a marathon interrogation he admitted taking a heavy backpack containing a bomb from an apartment in an eastern suburb of the capital to the Hua Lamphong railway station. There, he handed the bag to a man wearing a yellow shirt who was later filmed by a security camera placing it near the Erawan Shrine. 20 people were killed when the device exploded on 17 August.

"This place is where he met with the yellow shirt man to exchange a backpack," police spokesman Prawut Thavornsiri told reporters outside the train station.

"Yusufu said the backpack that he carried was heavy and it was a bomb."

Authorities have not confirmed Yusufu's nationality, saying only he is a foreigner, but local media reported he also held a Chinese passport issued in the restive Xinjiang region. He has not been formally charged yet.

Yusufu allegedly told detectives that Abudusataer, 27, had meetings with him and other members of the network behind the bombing to organise the attack, The Bangkok Post reported, adding that police believe the suspect left Thailand the day before the blast.

Police earlier arrested another suspect, also a foreign, which local media identified as Adem Karadag, saying he is a Turkish national. The Turkish-Chinese connection suggested by the investigation seems to substantiate the theory that China's Uighur extremists might be responsible for the attack.

Uighurs are a Turkic-speaking Muslim ethnic group related to Turks who have been leading a separatist struggle in China's Xinjiang. They have reasons to be angered at the Thai government, which recently handed back to Beijing more than 100 Uighur migrants who had sought asylum in Thailand.