A Pakistani security agency said on Friday it had arrested the father of a prominent political activist for spreading hate of the state on social media.
Muhammad Ismail was detained on Thursday after leaving a court in the northwestern city of Peshawar. A US official had earlier raised concern about harassment of Gulalai Ismail's family and the protection of rights.
The daughter, 32, is a prominent member of a group campaigning for the rights of the ethnic Pashtun minority, and is a vocal critic of Pakistan's military. Gulalai Ismail went into hiding earlier this year and emerged in the United States in September.
"The complaint is regarding ... hate speech and fake information against government institutions on Facebook and Twitter," the Federal Investigation Agency (FIA) said in a report.
Senior FIA official Mirwais Niaz said Muhammad Ismail had been brought before a court and remanded in custody for 14 days on Friday.
Gulalai Ismail was not immediately available for comment.
Her group, the Pashtun Tahaffuz Movement (PTM), has clashed with the military, which has accused it of disloyalty and being funded by Pakistan's regional rivals.
Earlier, before the authorities announced her father's arrest, Gulalai Ismail said she was worried about his fate after he had been picked up by unidentified men on Thursday.
"He was abducted by men wearing militia black dress, he was forced into a black-tinted vehicle," Ismail told Reuters in a text message. "We are very worried for our mother now and afraid that ... she will be arrested too," she said.
'HARASSMENT'
The US State Department's Bureau of South and Central Asian Affairs acting assistant secretary, Alice Wells, had earlier expressed her concern about the family.
"We are concerned by reports of the continued harassment of Gulalai Ismail's family, and her father's detention," Wells said on Twitter.
"We encourage Pakistan to uphold citizens' rights to peaceful assembly, expression, and due process."
The PTM has gained considerable support to the alarm of the military, which is wary of Pashtun nationalism in the strategically sensitive Pashtun lands along the Afghan border.
Pashtuns live on both sides of the border.
The Afghan Taliban are also predominately Pashtun, and have for years operated along the border, but the Islamists have been used by the Pakistani military in pursuit of its objectives in Afghanistan.
The US-backed Afghan government has expressed solidarity with the Pashtun nationalist movement.
The Pakistani military has accused the group of working against Pakistan's interest and getting funds from Afghanistan and old rival India. The group denies being opposed to the Pakistani state, saying it is only against terrorism.
The PTM, which has two seats in parliament, has accused of authorities of extrajudicial killings and enforced disappearances. Rights groups have called on Pakistan to investigate the disappearance and killing of PTM activists.
Damian Talbot