The perpetrators of last month's deadly Bangkok bombing were a network that trafficked Uighur Muslims and launched the attack in anger at Thailand's crackdown on the trade, police said on Tuesday.
No group has claimed responsibility for the Aug. 17 bombing at the Erawan Shrine that killed 20 people, an attack police chief Somyot Pumpanmuang ruled out as revenge for Thailand's forced repatriation in July of 109 Uighurs to China.
“It's about a human trafficking network that has been destroyed,” Somyot told reporters. “Deporting those 109 people, the Thai government did in accordance with international law. We also sent them to Turkey, not just China.”
Police have dampened speculation the bombers were members of international armed groups and have until now denied links to the Uighurs, who are mostly Muslim and say they flee China's western Xinjiang region due to persecution.
The Uighur issue is sensitive for the Thai government and any link between the bombing and their deportation at China's behest could expose it to criticism that its foreign policy may have resulted in the blast.
Somyot said the Bangkok bomb and the ransacking of the Thai consulate in Istanbul – which occurred the day after the deportation – were “for the same reason: illegal human migration, with an origin here and destination Turkey.”
“The cause of the bombing … Simply speaking, we destroyed their operation and they are angry,” he said.
Speculation that the blast was perpetrated by Uighurs was fueled by the use by several suspects of Chinese passports, at least one with Xinjiang as birthplace.
Many Uighurs seek passage to Turkey via Thailand. Some Turks recognize a common cultural and religious bond with Uighurs.
The self-professed Uighur government-in-exile, the World Uyghur Congress (WUC), on Tuesday slammed the Thai government for announcing that the attack was perpetrated by Uighurs “without conclusive evidence.”
“The Thai government has repeatedly gone back on its statement about potential perpetrators,” WUC spokesman Dilxat Rexit told Al Jazeera. Rexit said that what is believed to be the perpetrators' Chinese passports, found among several falsified travel documents, have not yet been authenticated.
“I hope that Thailand realizes that speaking on preliminary information without conclusive evidence is irresponsible and will serve to legitimize China's repression of Uighur civil liberties.”
Rexit condemned the attack, but said that the WUC had no information on potential perpetrators.
On Monday, police said that a key suspect in the bombing traveled on a Chinese passport and had fled to Turkey.
The suspect, identified as Abudureheman Abudusataer, left Thailand on Aug. 16 for Bangladesh, said national police spokesman Prawut Thavornsiri. He said information gathered by Thai police and Bangladeshi officials showed that the man departed Bangladesh's capital, Dhaka, on Aug. 30 and traveled to Istanbul as his final destination, via New Delhi and Abu Dhabi.
Thai police had previously said the man may have directed the bombing.
“He departed Dhaka on Aug. 30 for Delhi by Jet Airways,” Prawut said. “From Delhi, he continued his travel to Abu Dhabi, and from Abu Dhabi he traveled on Aug. 31 to Istanbul. This is his final destination. It's clear.”
Deputy Police Chief Chakthip Chaichinda said that a Pakistani and two Malaysians were arrested in recent days in Malaysia and are believed to have information on the blast, English-language Thai newspaper The Bangkok Post reported.
Thai police have come under criticism for not seeking outside help in their investigation.
The Bangkok Post said on Tuesday foreign cooperation was “not just desirable, but necessary.”
“Still, authorities remain reluctant to openly seek the easily available aid and advice from other countries,” it said.
Al Jazeera and wire services. Massoud Hayoun contributed reporting.