BANGKOK -- Police were searching Friday for clues to who set off two small bombs in Thailand's popular seaside resort town of Hua Hin, leaving at least one person dead and 20 others injured.

Reports on the websites of the Thai Rath newspaper and other media said the bombs were hidden in planters Thursday night on a busy street with open-front bars. The victims included Thais and foreign tourists, whose nationalities were not immediately known, according to the reports.

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

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The area is near many hotels and is popular with tourists.

It was not clear who was behind the attack, but the timing suggested it might be an effort to embarrass the military government that took power two years ago. 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.

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.

Prayuth's speech was to mark the success of a referendum Sunday that approved his government's proposed 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.

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, which Trang does not directly abut.

Thailand has been plagued by political violence, including several bombings, for much of the past decade.

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. His ouster set off sometimes bloody battles for power between his supporters and opponents, who include the military. His sister Yingluck Shinawatra, who became prime minister in 2011, was ousted in the 2014 army takeover.