Dozens of Uyghur men detained in Thailand after fleeing China may have been secretly deported to their home country, activists and rights groups said on Thursday, warning they could face torture and imprisonment on their return.

The Chinese embassy in Thailand has confirmed that a group of Uyghur men detained in Thailand for more than a decade have been deported to China.

At least 40 Uyghurs have been deported to China, the Thai authorities have confirmed, despite warnings from rights groups that they face possible torture and even death. The group is thought to have been flown back to China's Xinjiang region on Thursday,

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

Human rights groups warned that the Uyghurs, who were held in Bangkok for more than a decade, will face mistreatment from Chinese authorities back in Xinjiang.

Thailand's premier said on Thursday international standards and human rights principles must be followed, responding to activists' concerns that 48 Uyghurs held in the country for more than a decade had been secretly deported to China.

Thailand has deported at least 40 Uighurs to China’s Xinjiang region despite strong objections from activists and human rights

The detainees were part of a group of some 300 Uyghurs who fled China and were arrested in Thailand in 2014. Thailand deported more than 100 of them to China in 2015, drawing condemnation.

Rights groups criticized the Thai government for sending the Uyghurs, a persecuted Muslim minority, back to China, where they face the risk of torture and imprisonment.