Media playback is unsupported on your device Media caption Death sentence for UK tourist killers

Amnesty International has called for an independent investigation into allegations that two Burmese men, convicted of murdering two UK tourists, were tortured by Thai police.

Champa Patel from Amnesty said the police in Thailand had a "long and disturbing" history of using torture.

Convicted murderers Zaw Lin and Wai Phyo now face the death penalty.

A Thai court ruled on Thursday that they killed Hannah Witheridge, 23, and David Miller, 24.

The British backpackers' bodies were found on a Koh Tao island beach in September 2014.

Miss Witheridge, from Hemsby, Norfolk, had been raped before she was killed, while Mr Miller, of Leeds, had been hit over the head before drowning in the sea.

Lawyers for the defendants - both aged 22 and migrants from Myanmar - have said they will appeal.

The accused, both bar workers, retracted their initial confessions, claiming police had tortured them, an allegation supported by human rights campaigners.

A flawed and muddled investigation

Families talk of 'senseless' killings

Media playback is unsupported on your device Media caption David Miller's brother, Michael, said the case against the accused men 'was no shambles'

But standing outside court shortly after the verdict Mr Miller's brother Michael said justice had "been delivered", and described the evidence against Lin and Phyo as "absolutely overwhelming".

He also called for campaigners to respect the court's decision.

Torture 'credible'

But Mr Patel, who is Amnesty International's director for south-east Asia, said the torture claims required an independent investigation, which the police themselves should not be in charge of.

"The Thai police force has a long and disturbing track record of using torture and other forms of ill-treatment to extract 'confessions'," he added.

"This is far from an isolated case.

"The Thai authorities must start taking concrete steps to stamp out torture, not just paying lip service to doing so," he added.

Image copyright EPA Image caption Wai Phyo (left) and Zaw Lin (right) retracted their initial confessions

The human rights campaign group also said that in its own investigation of the case, the Thai National Human Rights Commission found the allegations of torture to be credible.

DNA evidence

Earlier, Miss Witheridge's family said they needed time "to digest the outcome of the trial verdict".

During the trial prosecutors said DNA evidence collected from cigarette butts, a condom and the bodies of the victims, linked Lin and Phyo to the deaths.

But lawyers defending the accused argued DNA from a garden hoe - allegedly used as the murder weapon - did not match samples taken from the men.

They also claimed evidence had been mishandled by police and the pair's confessions were the result of "systematic abuse" of migrants in the area.

Thailand has not carried out any executions since 2009, when two executions took place, according to a death penalty database collated by Cornell Law School in the US.

The victims met on Koh Tao while staying in the same hotel.

The family of Mr Miller attended the hearing but relatives of Miss Witheridge did not travel to Thailand for the verdicts.