Hong Kong authorities said no tour groups from the city had been affected by the attacks, while travel agents warned people to be vigilant.

Thai Prime Minister Prayuth Chan-ocha said the bombings were an attempt to “create chaos”.

“Why have the bombs occurred as our country is heading towards stability, a better economy and tourism – and who did it? You have to find out,” he said.

Thursday night’s explosions took place thirty minutes apart in the bar district of the popular beach town, the latest incident to threaten Thailand’s reputation as a holidaymaker’s paradise.

Small blasts are common in Thailand during times of heightened political tension, but there have been few such incidents in the past year and it is rare for tourists – a key source of income for the kingdom – to be targeted.

Officials said they were looking into motivations behind the latest blasts, which hit around after 10:00 pm and killed one Thai woman selling papaya salad.

“The type of bomb is still under investigation,” Hua Hin’s police chief, Sitthichai Srisopacharoenrat, said after the twin blasts.

“One Thai woman was killed and altogether from the two bombs 19 people were injured,” said another local officer.

“Three are in serious condition and seven of the injured are foreigners – four women and three men,” he said, adding that the two blast sites were 50 metres apart.

Photos showed emergency workers evacuating victims from the area on stretchers and foreign tourists with minor cuts and injuries gathered at a local hospital.

China’s state media reported that there were no Chinese citizens killed or injured in the bombings, citing the embassy in Bangkok.

In Hong Kong, Travel Industry Council Executive Director Joseph Tung Yiu-chung told the South China Morning Post that there were several Hong Kong tour groups with about 130 people in Hua Hin when the blasts happened and all of them were safe. Another 50 tours of about 1,200 people are scheduled to visit the town throughout the rest of the month. Tung said the council had not received any requests for assistance from travel agents.

“We have advised tour guides to keep tourists [in Thailand] away from [crowds] at night,” he said.

Jason Wong, a director at Hong Thai Travel, said a tour with some 30 people organised by the company are in Hua Hin and all of them are safe. They are scheduled to fly back to Hong Kong on Friday as scheduled. Wong said the explosions would not affect the company’s tours to Thailand.

EGL Tours executive director Steve Heun said a 29-person tour to Hua Hin next week will go ahead as the government has not issued any more travel alerts. He said it was too early to tell whether the business of Thailand trips would be affected and told people visiting the country to be vigilant.

The Hong Kong government issued a “yellow” outbound travel alert to Thailand in September 2015, a month after a bomb exploded near Bangkok’s Erawan Shrine, killing 20 people. The yellow alert is the lowest of three risk levels for Hong Kong travellers and means threats exists and travellers should be alert. The Security Bureau advised people who are planning to visit the country or are already there to be careful and pay attention to announcements by local authorities and also avoid large groups of people.

Hua Hin is an upscale resort town about 200km south of Bangkok, popular with both local and foreign tourists.

It is also home to a palace for years frequented by Thailand’s revered King Bhumibol Adulyadej, the world’s longest reigning monarch.

The 88-year-old is currently sick in hospital in Bangkok.

The explosions come ahead of a long holiday weekend in the kingdom, with many people travelling as Thais prepare to celebrate Queen Sirikit’s 84th birthday on Friday.

Thailand’s reputation as the “Land of Smiles” has suffered in recent years amid frequent road accidents, crimes against foreigners and political unrest, but tourists continue to flock to the its sandy beaches and famed temples.

The kingdom is expecting a record 32 million visitors in 2016, with the tourism industry a bright spot accounting for at least a tenth of the otherwise lacklustre economy.

Thai authorities have accused two Uygur men from western China of the bombing, which was the deadliest assault of its kind in recent years.

The two men have both denied involvement in the attack and their trial is set to begin later this month.

Thailand’s military junta, which seized power in 2014 after a decade of at times deadly political unrest, has touted increased stability in the kingdom as a major accomplishment of its rule.

But the generals have been unable to quell a festering Islamic insurgency in the three most southern provinces – nearly 1,000km away from Hua Hin.

The conflict is largely contained to the far south region but has occasionally spilled into other areas.

Business conflicts have also been known to trigger small incidents of violence in Thailand.

Earlier Thursday local media reported that several people were injured by a small explosion at a market in Trang province.

Additional reporting by Nikki Sun