A series of bomb attacks across central and southern Thailand that killed 4 people and injured over 30 others, including foreign tourists, was likely to be the work of "local elements," Thai police said Friday.
Speaking from the National Police Headquarters in Bangkok, Police Chief Chakthip Chaijinda told reporters that he believed they were carried out by people dissatisfied with the political situation in Thailand, which is currently in its third year under a military government.
He said it could have been carried out by opponents of a military-drafted constitution, which was approved in a referendum last week.
"You have to look at where the attacks occurred, all these provinces voted for [the military constitution]," he said. "This is just my opinion, but these attacks were in relation to the political developments."
The multiple bomb attacks struck tourist destinations and government buildings across five provinces in less than 24 hours.
In one of the blasts, which struck around midnight in the busy seaside resort of Hua Hin, three Germans, three Italians, three Dutch citizens and one Austrian were injured, according to embassy and police officials.
All those wounded were taken to hospital in Hua Hin, also well known as the location of the Thai royal family's summer palace.
The German Foreign Ministry issued a travel warning for Thailand saying that its nationals should exercise extreme caution if visiting the country.
Security was increased after the overnight and early morning attacks. Police dogs and soldiers were seen patrolling railway stations and government installations across the capital of Bangkok.
Nittinai Sirismatthakarn, president of Airports of Thailand, told dpa that security was increased to its highest level and advised passengers to leave early to catch their flights.
The junta instructed security personnel to increase vigilance ahead of Queen Sirikit of Thailand's birthday celebrations on Friday, spokesman Winthai Suvaree said.
"We will not let people with bad intentions towards the country dictate the situation," Winthai told reporters.
The attacks were not "terrorism-related," Thai police said.
"Thailand has no territorial or religious quarrel with anyone. This is not an act of terrorism but an act of local sabotage," said police spokesman Piyaphan Phingmuang.
Two explosions targeted police stations in the southern province of Surat Thani around 8 am (0100 GMT) on Friday. One person was killed.
Another bomb attack hit the tourist resort of Phuket around 9 am. The explosion occurred near Patong beach, which is popular with foreign tourists. The blast injured one taxi driver.
A third bomb attack targeted a tourist area in southern Phang Nga province but no one was injured.
One person was killed and three more were injured in a bomb attack around 9 am in the seaside resort of Hua Hin, about 200 kilometres south-west of Bangkok.
The incident occurred less than 12 hours after a separate bomb attack in the same city killed one person and injured 20 more, including the 10 foreigners.
"The bombings have the same attack profile," Army General Danai Kritmethavee told reporters. "We believe at this time that this was a coordinated attack."
One person was also killed Thursday evening in a bomb attack in the southern province of Trang, 850 kilometres south of Bangkok
"These attacks are aimed at creating unrest in the country," Deputy Prime Minister Prawit Wongsuwan told reporters Friday morning.
Prime Minister Prayut Chan-o-cha said "we have to focus on not creating panic among the people and restoring law and order."
Authorities provided little evidence indicating who was behind the attacks, which come as Thais marked a long weekend to celebrate Queen Sirikit's 84th birthday, also Mother's Day in Thailand.
Many Thais either return home or spend the extended break at seaside resorts like Hua Hin, although pictures online suggested that the streets of Hua Hin were mostly empty early Friday.
Thailand sees regular bomb attacks, but rarely beyond its most southern areas. Since 2004, an insurgent movement to create an independent state in three southern Muslim-majority provinces has resulted in 6,200 deaths and 11,000 people injured.
In five days' time the country will mark one year since one of its worst bomb attacks. The bombing of the Erawan shrine on August 17 last year killed 20 people, mostly tourists.