Human rights groups in Pakistan are demanding that authorities immediately find four missing social media activists who have been critical of the government's counter-extremism efforts.
Relatives say that Salman Haider, a poet and activist, disappeared on Friday. His wife received a text message on her cell phone to go and collect Haider's car from a roadside on the outskirts of the capital, Islamabad.
An independent watchdog group, the Human Rights Commission of Pakistan, or HRCP, identified the others as Waqas Goraya, Asim Saeed and Ahmed Raza Naseer. They also vanished last week.
The men ran popular social media accounts.
No group has claimed responsibility for the disappearances and it was not known whether they are linked.
The Interior Ministry Monday ordered police to urgently determine the whereabouts of the four men.
The activists are known for airing their views, sometime critical of authority, extremism and intolerance, on social media, HRCP noted in a statement issued Monday, saying it was unable to determine the actors behind the disappearances.
"But Pakistan has never been a particularly safe country for rights activists. Many have been killed, injured, abducted and threatened for their work. Unfortunately, these actions have not always come from non-state quarters," the watchdog group said.
The opposition Pakistan Peoples Party has demanded that parliament seek answers from the government on the disappearances, calling them a planned and coordinated crackdown to silence voices critical of state policies.
Pakistani rights groups and activists have announced countrywide protests to press authorities to find the men quickly.
Pakistani state intelligence agencies are often accused of illegally detaining people in the name of fighting terrorism and in some cases people have spent years in detention, with relatives not knowing the fate of their loved ones.
Human rights groups have approached the country's supreme court in recent years seeking its intervention to recover disappeared people. The legal pressure prompted authorities to release scores of detainees to rejoin their families.