Bangkok: Thai police hunting the culprits behind a wave of deadly blasts that rocked tourist destinations and killed four said Sunday they "know who was behind" the attacks.
Police said two men have been held for questioning over the blasts in Hua Hin -- a resort town struck by four bombs -- with a third questioned over a suspected arson attack in Nakhon Si Thammarat province.
Officers, who have ruled out terrorism, said the investigation was preliminary and refused to identify the detained as suspects, or offer a possible motive.
Some analysts suggest the blasts are most likely connected to a simmering insurgency in Thailand`s southern tip, pitting Muslim rebels against the state, but police have said foreign or local terrorist groups were not behind the attacks and have instead labelled them act of "local sabotage".
"Our investigation is progressing. We know who was behind it," deputy police spokesman Piyapan Pingmuang told AFP Sunday, declining to provide further details.
No one has claimed responsibility for at least 11 small explosives and series of suspected arson attacks that ripped across core tourist hubs Thursday night and Friday morning, killing four locals and wounding dozens, including European tourists.
Thailand has also been wracked by a bitter power struggle between a military-allied elite and populist forces loyal to the ousted government.
The recent blasts, many of them detonated by mobile phones, came as an affront to a junta that prides itself on bringing a measure of stability to Thailand since its 2014 power grab.
The attacks also came only days after the junta won a referendum vote on a new charter it drafted.
The document, which critics said would make Thailand less democratic, was approved by voters living in the bomb-hit provinces.
The only regions to reject it were the north and northeast -- strongholds of the ousted government -- and the three insurgent-torn provinces in the deep south.
The southern conflict zone -- the only Muslim-majority area in Buddhist Thailand -- sees regular bombings and shootings, but the violence seldom leaks outside the three provinces bordering Malaysia.
The insurgency has killed more than 6,500 in the past decade but rarely makes international news and falls on the sidelines of Thailand`s core political crisis.
Tourist hubs have also been spared turbulence from the kingdom`s two rival political factions, who have held repeated rounds of mass protests in Bangkok over the past decade, often marred by streetside gunfights and grenade attacks.
But the violence has not matched the coordinated nature of the recent bombings.
The attacks in tourist towns threaten a vital source of income for the country. Thailand was hoping for a record 32 million visitors this year.
The sector accounts for at least 10 percent of Thailand`s economy, which the military government has struggled to invigorate since its 2014 power grab.