U.S. Secretary of State Marco Rubio on Thursday condemned Thailand's return of at least 40 Uyghurs to China, where Washington says members of the Muslim group have faced genocide.

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.

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.