Bangkok, Thailand: Two Chinese Uighurs said by police to have admitted a deadly bombing at a Bangkok shrine denied involvement in the unprecedented attack when they appeared handcuffed and shackled in a Thai court on Tuesday.

Bilal Mohammed, also known as Adem Karadag, and Yusufu Mieraili were barefoot during the plea hearing in the military court.

A judge read the charges of attempted and premeditated murder, possession of illegal weapons and illegal entry to the pair through a Uighur translator.

Both said they were not guilty of the bombing charges, although Mohammed conceded he had entered the country illegally.

‘I’m not guilty... but I’ve been in prison for six months,’ a disconsolate-looking Mieraili added.

The August 17 bomb killed 20 people and wounded scores more at a shrine popular with ethnic Chinese tourists.

A convincing motive has yet to be established for an attack that dented Thailand’s key tourist industry and spread fear through a politically febrile country that is under military rule.

Police say the two men initially admitted their roles in the bombing.

Mohammed, who told the court he was 31 and a Chinese citizen from the Uighur ethnic minority, is accused of being the man seen in CCTV footage wearing a yellow T-shirt and placing a backpack at the Erawan shrine moments before the explosion.

Mieraili, 26 and also a Chinese Uighur, was the second of the two to be arrested.

During questioning authorities say he confessed to delivering the backpack bomb to another man who planted the device.

Motive a mystery

Police chief Chakthip Chaijinda said it was the ‘defendants’ right’ to retract their earlier confession.

‘But we have witnesses and clear evidence to prosecute them,’ he told reporters.

Mohammed was arrested in late August a a block of flats in a Bangkok suburb.

Photographs released at the time showed him surrounded by bomb-making paraphernalia and dozens of fake Turkish passports.

Shortly after the arrest, his lawyer told reporters that Mohammed admitted carrying out the bombing on the orders of an apparent mastermind—one of more than a dozen suspects, both foreign and Thai, still at large.

But before Tuesday’s hearing the lawyer, Schoochart Kanpai, alleged his client had been tortured to confess to the crime.

The pair have been held at a barracks in Bangkok, appearing only for a re-enactment of the bombing and at their November indictment.

Mystery still surrounds the motive for the attack, in which the majority of the dead were ethnic Chinese tourists.

Speculation has centred on a link to militants or supporters of the Uighurs, an ethnic group who say they face severe persecution in China, after Thailand forcibly repatriated 109 of the minority last July.

Mohammed’s lawyer says he is a Chinese Uighur whose family settled in Turkey while Mieraili is a Chinese passport-holder of Uighur ethnicity.

Thai authorities have rejected the theory that the bomb was a revenge attack for the deportations.

Instead investigators have stuck to the line that it was carried out by a people-smuggling gang angered by a crackdown on its business—a theory many analysts have questioned.

Until Tuesday’s hearing the case had largely dropped off the news cycle, easing the pressure on authorities to arrest further suspects despite fears of a bungled investigation.

Police awarded themselves a $84,000 reward after the arrest of Mohammed, even though he had not even been charged at the time.