China has assured Thailand that 40 Chinese Uyghurs it returned on Thursday would be looked after, Thailand's defense minister said, confirming a secretive predawn deportation that the United Nations and human rights groups condemned.

The move came despite urging by United Nations human rights experts not to send back the Uyghurs Thailand has held in detention for a decade, warning they were at risk of torture, ill-treatment and "irreparable harm" if returned.

The Uyghurs were sent back in accordance with international standards, Phumtham Wechayachai said, in Thailand's first confirmation of the deportation, its second in the past decade.