BANGKOK: Thailand should be commended for its handling of its return of 40 Uyghur Muslims to China, a deputy premier said on Friday, as his country endured a torrent of international condemnation over its secretive deportation.

The 40 Uyghurs who had been held in Thailand for a decade were sent back to China in a pre-dawn operation on Thursday, defying calls from United Nations human rights experts who said they would be at risk of torture, ill-treatment and "irreparable harm" if returned.

The European Union and the U.N. refugee agency said Thailand had clearly violated its international obligations, while U.S. Secretary of State Marco Rubio expressed alarm at the forced return of Uyghurs by a U.S. ally to a country where he said the ethnic minority had faced genocide, forced labour and crimes against humanity.

The move also drew a rebuke from Australia.

Thai ministers on Friday said measures were being taken to ensure the wellbeing of those returned, including periodic inspections starting from next week.

"Thailand should be commended for managing this problem," Defence Minister and deputy premier Phumtham Wechayachai told a press conference.

"This is done out of goodwill of the Thai government and not ill intent ... it is a good thing to get them out of detention so they can return to their normal lives with relatives, husbands, wives and children."

Phumtham said the Uyghurs returned voluntarily and Thailand had received reassurance from China they would be cared for and not mistreated.

'LIES OF THE CENTURY'

Rights groups accuse Beijing of widespread abuses of Uyghurs, a mainly Muslim ethnic minority numbering about 10 million in the western region of Xinjiang. China denies any abuses.

Asked on Friday about international criticism of the deportation, China's foreign ministry said it firmly opposed "groundless accusations" and interference in its internal affairs.

Spokesperson Lin Jian told a regular briefing Rubio's allegations of genocide and forced labour were "blatant lies of the century".

The 40 Uyghurs were part of a group of 300 who fled China and were arrested in Thailand in 2014. Some were sent back to China and others to Turkey, with the rest kept in Thai custody.

Thai Justice Minister Tawee Sodsong said the foreign minister would be among those visiting the Uyghurs returned to China.

"We will make inspections from time to time ... we will go see for ourselves," he said, adding Thailand would seek to bring media also.

The deportation of the Uyghurs was Thailand's second in a decade and some diplomats and security analysts believe the July 2015 transfer of 100 Uyghurs to China led to the bombing a month later of a busy Bangkok shrine that killed 20 people in the worst attack of its kind on Thai soil.

Thai authorities at the time concluded the attack was linked to their crackdown on a human trafficking ring, without specifically linking the group to the Uyghurs. Two ethnic Uyghur men were arrested in connection with the attack and their trial is proceeding, despite repeated delays.

Tawee said there were five other Uyghurs serving prison sentences in Thailand until 2029 following convictions in unrelated criminal cases.