BANGKOK (Reuters) - Thai police on Sunday defended their investigation into the 2014 murder of two British tourists after a court sentenced two men from Myanmar to death for the killings, prompting protests in Myanmar and Thailand.

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Hundreds called for the release of migrant workers Zaw Lin and Win Zaw Htun in protests over the weekend outside the Thai Embassy in Yangon, Myanmar’s biggest city, and in towns around Thailand.

Protesters said the two men were used as scapegoats by authorities in an effort to close the high-profile case.

On Thursday, a court on Koh Samui island convicted the pair of the murder of backpackers Hannah Witheridge, 23, and David Miller, 24. The tourists were found bludgeoned to death on a beach on the nearby holiday island of Koh Tao.

The killings dented Thailand’s image as a easy-going tourist haven and raised questions about police competency.

Zaw Lin and Win Zaw Htun were arrested following mounting pressure on police to solve the case. Police said the two confessed to the crime, but both later retracted their confessions, which they said had been made under duress.

The police investigation was mired in controversy, including allegations of incompetence, torture and mishandling of crucial DNA evidence.

During the trial, a judge dismissed allegations of torture, saying there was no evidence it took place.

On Sunday, Thai police spokesman Dejnarong Suthicharnbancha told reporters in Bangkok “I would like to reassure that the investigation process of police was transparent… and of a standard that is acceptable.”

Deputy police spokesman Piyaphand Pingmuang said “we cannot undo the investigation”. He asked Thai and Myanmar nationals not to join demonstrations against the verdict.

“Some groups are trying to make this a political matter and about diplomatic ties, but there are no issues because Thailand has communicated with the Myanmar government to create understanding on this matter,” Piyaphand said.

In a New Year message to Thai Defense Minister General Prawit Wongsuwan, Myanmar’s Commander-in-Chief Senior General Min Aung Hlaing requested that evidence in the case be reviewed.

“It is more important that an innocent person should not be convicted rather than a guilty person not be punished,” he said.

Miller’s family, in a statement to media on the court verdict, defended the work of Thai police, saying a “methodical and thorough” investigation was conducted.