A series of blasts hit three of the most popular tourist resorts in Thailand on Thursday and Friday, killing two people and wounding dozens, just days after the country voted to accept a military-backed constitution in a referendum.
Twin blasts hit the upscale resort of Hua Hin, about 200 km (125 miles) south of Bangkok, on Friday morning just hours after two bombs killed one person and wounded 21 late on Thursday.
Hua Hin is home to the Klai Kangwon royal palace, which translates as "Far from Worries Palace", where King Bhumibol Adulayadej, the world's longest reigning monarch, and his wife, Queen Sirikit, have often stayed in recent years.
Friday was a public holiday in Thailand to mark the queen's birthday, which is celebrated as Mother's Day.
One person died and three people were wounded in one of the Friday morning blasts near a central clock tower in Hua Hin, deputy police spokesman Police Colonel Krisana Pattanacharoen told reporters in Bangkok.
Two small bombs exploded in the tourist beach town of Patong on Phuket island, and two more in Phang Nga, another tourist region in the south, on Friday, police said. One Thai man was lightly wounded in Patong, police said.
Police believe the blasts were acts of "local sabotage" and not linked to international militants, Krisana told reporters.
"It's too soon to jump to any conclusion," he said "But what we know for sure is that the incidents are not linked directly to any kinds of terrorism, in fact it's local sabotage and we are trying to identify those responsible behind the scenes.
"There are no conflicts in the country that may lead to terrorists being in the country. That's why we can say that these incidents are not terrorist attacks," he said.
Police Explosive Ordnance Disposal (EOD) official inspects the site of a bomb blast in Hua Hin, south of Bangkok, Thailand, in this still image taken from video August 12, 2016.
Police also said they have not found any evidence that the blasts were coordinated or whether they were related to an insurgency in Muslim-majority provinces in southern Thailand.
The attacks are bad news for Thailand's tourist sector, which has been one of the few bright spots in a sluggish economy.
Tourism accounts for about 10 percent of gross domestic product and Thailand is expecting a record 32 million visitors this year.
Australia issued a travel advisory saying Australians should "exercise a high degree of caution" and warned: "Further explosions in any part of Thailand are possible."
The Friday morning blasts in Hua Hin came after a bomb exploded near a bar in the town late on Thursday that killed one Thai woman and wounded 21 people, Krisana said.
Nine of those injured in Thursday night's twin blasts in Hua Hin were foreigners, the town's deputy police chief, Same Yousamran, said. The two explosions were detonated by a mobile device, police said. The first took place 20 minutes earlier and about 50 metres from the second, but injured nobody.
Such twin blasts are common in the three Muslim-majority southernmost provinces of Thailand, where a long-running insurgency intensified in 2004, with more than 6,500 people killed since then.
The three provinces near the border with Muslim-majority Malaysia soundly rejected the referendum on the new military-backed constitution which passed convincingly in most of the rest of the country in Sunday's vote.
Violence has occasionally spilled over to areas outside the three provinces, which were part of a Malay sultanate until it was annexed by Buddhist-majority Thailand a century ago.
Hua Hin, Phuket and Phang Nga are far from the usual conflict zone, where attacks are typically aimed at the security forces and government representatives, not tourists.
In a separate incident on Friday, media reported two bombs had exploded in the southern province of Surat Thani, killing one person and wounding five. That came after a blast in Trang, also in the south, on Thursday, in which one person died and seven were wounded.
Authorities defused two explosive devices in Phuket on Wednesday, police said.
A damaged public telephone booth is seen at the site of a bomb blast in Hua Hin, south of Bangkok, Thailand, in this still image taken from video August 12, 2016. REUTERS/REUTERS TV.
The head of Interpol in Thailand, Police Major General Apichat Suriboonya, told Reuters he needed more information before deciding "whether it is terrorism or not".
"But the thing is, if you observe the bombs, they are not targeted to kill people but to send a message to some groups. It could be a domestic issue."
Small bombs have been used frequently for attacks during periods of unrest over the past decade of political turmoil in Thailand.
However, such attacks have been rare since the military seized power in a 2014 coup.
The latest bombings came almost a year after an attack on a Hindu shrine thronged with tourists in central Bangkok killed 20 people and wounded more than 120. Police have accused two ethnic Uighur Muslims from China for the Aug. 17, 2015, attack.
Police also ruled out the possibility international militants may have been responsible for that attack, and said the perpetrators were members of a network that trafficked Uighurs and launched the attack in anger at a crackdown.
Analysts, diplomats and even some officials suspected the attack was linked to sympathisers of China's Uighur minority angered by the Thai junta's deportation of more than 100 Uighurs to China the previous month.
King Bhumibol and the queen are both in hospital in Bangkok and have not stayed recently at their palace in Hua Hin. Check points have been established and security beefed up around Hua Hin and the palace there.
The king has received treatment for an infection over the past month in hospital, the Royal Household Bureau said on Aug. 1. Concern about the health of the king and nervousness over the succession have played into the country's political tensions.