PESHAWAR, Pakistan — A prominent rights group Thursday asked Pakistan to immediately disclose the whereabouts of an activist who authorities acknowledged was being held on a treason charge months after his disappearance.

Pakistani rights activist Idris Khattak, who worked for both Amnesty International and Human Rights Watch, went missing along with his driver on Nov. 13 last year. Later, his driver told his family that Khattak was taken by unidentified men from his car while they were traveling in the country's volatile northwest.

The request for information came from Amnesty.

Pakistan maintained silence over Khattak's disappearance until June, when the Ministry of Defense responded to his family's complaint. The ministry told a court that Khattak was in custody and faced a treason charge, which is punishable by death.

Amnesty International, on the anniversary of Khattak's disappearance, in a statement said the man "worked extensively to tackle enforced disappearance" before he himself went missing last year.

It asked Pakistan to lift the veil of secrecy surrounding his case.

"A year after he was taken from them, Idris Khattak's family remain completely in the dark about where he is being kept, his state of health, and the legal process he is being put through, if any," said Omar Waraich, the head of South Asia at Amnesty International.

"The Pakistani authorities must end this intolerable situation by disclosing his whereabouts and allowing him regular access to his family and lawyer," he added.

Waraich asked Pakistan to bring Khattak before a civilian court. The country has witnessed an intensified crackdown on human rights defenders, journalists and members of civil society in recent years.