Human Rights Watch has called on the Thai government to release the whereabouts of a government critic who has not been seen since his arrest last week.
HRW says Sarawut Bamrungkittikhun was arrested March 9 at his home in Surat Thani province.
The rights group describes Bamrungkittikhun as an "outspoken critic" who runs an anti-junta Facebook page.
HRW says the ruling Thai junta has "officially denied" knowledge of his arrest and location, raising what it says are grave concerns of an enforced disappearance.
"Thailand's junta has repeatedly flouted international legal protections by secretly detaining critics of the government," said Brad Adams, HRW's Asia director.
"The government should put to rest fears that Sarawut has been forcible disappeared by immediately disclosing his whereabouts, allowing his family and lawyers access and releasing him if he hasn't been charged."
Under the National Council for Peace and Order rules, security officers can detain a person for a maximum period of seven days before issuing formal charges.
HRW says there are reports that Sarawut was brought to Bangkok and put in detention at a prison facility inside an army camp, but they have not been verified.