BANGKOK: Thai police have confirmed that two more bombs have gone off in another city, killing one person, in the latest in a string of blasts to hit the country, including two in the seaside resort town of Hua Hin that killed one and wounded nearly 20 more people — half of them foreigners.

It was not clear who was behind the attacks. But the timing suggested it could have been carried out by opponents of the nation's ruling junta, whose leadership last weekend organized a successful referendum on new constitution that critics say will bolster the military's power for years to come.

Police General Apichart Boonsriroj said the bombs exploded in front of two police stations half an hour apart in Surat Thani in southern Thailand.

Four people were also wounded in the Friday morning blasts that came as police were searching for clues to who set off the two small bombs in Hua Hin.

The Hua Hin bombs were set off late Thursday by remote control, half an hour apart, according to Pol. Gen. Sithichai Srisopacharoenrath, the superintendent of police in Hua Hin, and his deputy, Lieutenant General Samer Yousamran.

Sithichai said both devices were hidden inside plants on a busy street filled with restaurants, bars and food vendors that is popular with tourists and local residents.

Sithichai said one Samsung cell phone had been recovered that they believe was used to detonate at least one the bombs.

The fatality was described in Thai media as a female street food vendor. Several of the injured were in serious condition, the reports said.

Police Lt Chaiyot Tisawong, an officer in Hua Hin, said 10 of the injured were foreigners. Their nationalities were not immediately known.

The incident took place on the eve of the birthday of Queen Sirikit in a town where she and King Bhumibol Adulyadej maintain a summer palace. The ruling junta has declared that defending the monarchy is its priority, especially as there is concern about the process to succeed the ailing 88-year-old king, who is the world's longest reigning monarch.

Another bombing took place earlier Thursday in the southern province of Trang, killing one person and injuring six, according to Thai press reports. It was unclear if it was related to the Hua Hin blasts.

Trang is on the fringes of Thailand's deep south, where a low-level Muslim separatist insurgency had killed more than 5,000 people since 2004. Almost all the violence has been in the three southernmost provinces.

Thailand has been plagued by political violence, including several bombings, since the populist billionaire Thaksin Shinawatra was ousted as prime minister in a 2006 military coup after demonstrations accused him of corruption, abuse of power and insulting King Bhumibol.

Thaksin's ouster set off sometimes bloody battles for power between his supporters and opponents, who include the military. The government of his sister Yingluck Shinawatra, who became prime minister in 2011, was ousted in the country's last coup in 2014.

On Sunday, Thai voters approved a referendum on a new constitution that is supposed to lead to an election next year. Critics say it is undemocratic and is fashioned to keep the military in control for at least five more years even if a free election is held.

In a speech Wednesday night, junta chief and Prime Minister Prayuth Chan-ocha on Wednesday night took credit for bringing stability back to Thailand after an extended period of unrest.