Thai police have said at least 20 people were involved in the deadly bombings which hit the country in early August. Authorities believe many of those responsible came from the Muslim-majority southern provinces.
National police chief Jakthip Chaijinda told reporters on Monday that investigators believe a group of "more than 20 people" were behind the coordinated attacks.
The explosions on August 11 and 12 targeted popular tourist spots across several southern Thai provinces, just days after the nation voted to approve a military junta-backed constitution. Four people were killed in the attacks, while dozens of others were wounded.
"We know where they came from, where they went," Jakthip told reporters, without giving further details.
No group has claimed responsibility but police and the government ruled out any link to foreign militants within hours of the attacks, insisting the perpetrators were home-grown.
Asked on Monday whether the suspects were Thai nationals Jakthip replied: "They are not Buddhists."
"Most of them are from the area of the southern border provinces police operation centre," he said, referencing a policing area that encompasses the Muslim-majority southernmost region.
A movement to create an independent state in three majority-Muslim provinces in the south of Thailand has existed for decades, but resurged in 2004.
Police have so far issued one arrest warrant in relation to the most recent attacks. Authorities said last week that DNA evidence collected at one of the blast sites in Phuket matched with a person involved in a similar attack carried out in 2004 in southern Thailand.
According to monitoring group Deep South Watch, more than 6,500 people have been killed in the region due to bombings, shootings and arson attacks since 2004.
ksb/rc (Reuters, AFP)