Bangkok, Aug 29 (IANS): Thailand's Supreme Court on Thursday upheld the death sentences of two Myanmar citizens accused of killing two British backpackers in 2014 on the popular tourist island of Koh Tao.

On December 25, 2015 migrant workers Zaw Lin and Win Zaw Thun were found guilty by a local court of murdering Hannah Witheridge, 23, and David Miller, 24, as well as for raping Witheridge, Efe news reported.

The police investigation was widely questioned and led to allegations that the men were used as scapegoats.

The pair initially confessed to the crime, committed in September 2014, but later withdrew their confessions and alleged that they had been tortured and threatened in police custody.

"I respect the verdict delivered by Thailand's Supreme Court in the Koh Tao murder case today," tweeted migrant workers' rights activist Andy Hall, who served as the international affairs advisor to the legal defence team.

"However, after having seen so much of the evidence presented in the court or otherwise in this case... I consider that the death penalty sentence and conviction of the two accused... should instead have been reversed and quashed by the Supreme Court," he added.

Miller died as a result drowning and severe blows to the head, while Witheridge was raped and bludgeoned to death.

The convicts could seek a royal pardon from execution, which if granted would convert the punishment to life imprisonment.