Human rights activists in Pakistan say security agencies abducted one of their leading campaigners who is now in police custody in Islamabad.
Mr Khawaja wrote a letter from his cell describing his abduction
Khalid Khawaja, who heads the Defence of Human Rights group, was abducted on his way to morning prayers at a city mosque early on Friday, activists said.
He appeared in court on Saturday and was remanded in custody for distributing banned literature.
Activists say abductions by the security agencies have become routine.
Mr Khawaja, who is a former intelligence officer, has been campaigning for the release of dozens of people who have gone missing in Pakistan.
Hundreds of Pakistanis have disappeared since 2001
Following news of his abduction, Human Rights Watch described his disappearance as "suspicious" and urged the authorities to reveal his whereabouts.
The next day, Mr Khawaja was brought before a court in Islamabad and remanded in custody for three days. He denies the charges of distributing banned literature.
From his cell, he wrote to his colleagues describing his abduction.
He said his abductors had been dressed in civilian clothes.
He was blindfolded and forced into a vehicle before being taken to an unknown location where he was interrogated by different people until late at night, he said.
Around midnight he was brought to a police station in the Aabpara district of the capital.
The police officer "did not know what to do with me and probably was waiting for instructions until midday".
The Human Rights Commission of Pakistan says 200 people are "missing" who it believes are in the custody of the security agencies.
Recently, the Supreme Court forced the government to acknowledge it was holding at least 25 such persons.
Many of those released from custody have alleged that they were held by military intelligence agencies.