A human rights activist in Pakistan has disappeared from jail premises hours before he was due to be released.
Mr Khawaja has been a thorn in the side of the Pakistan government
Khalid Khawaja was due to be freed on Thursday after being granted bail by a judge in Rawalpindi.
His colleagues say jail authorities handed him over to intelligence officials on Wednesday night.
Mr Khawaja was detained in January. He is a leader in the campaign to find scores of people alleged to have been "disappeared" by the authorities.
Hundreds are missing in Pakistan after being abducted by security agencies, human rights groups say.
It is not clear who took Mr Khawaja away from the Adiala jail in Rawalpindi.
On Thursday, Amna Janjua, a member of Mr Khawaja's Defence of Human Rights group, told the BBC: "We received an anonymous call yesterday evening that he's being taken away from the jail illegally".
But by the time she and Mr Khawaja's family members got there, he had already gone.
Mrs Janjua says that she then approached the jail superintendent, Noor-ul-Hasan.
She says he told her that the jail authorities had been instructed by the home secretary to hand over Mr Khawaja.
"He said that he was only following orders and there was nothing he could about it."
She added that the superintendent did not tell them where Mr Khawaja had been taken or in whose custody he was being held.
However, Mrs Janjua says that his family later received another anonymous call telling them he had been taken to the Attock fort.
Attock fort is a notorious military prison used by intelligence agencies, primarily the ISI, in a northern Pakistani town of the same name.
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 people have disappeared since 2001, rights groups say
Following news of his initial abduction on 26 January, Human Rights Watch described his disappearance as "suspicious" and urged the authorities to reveal his whereabouts.
The organisation now says that it finds "Khalid Khawaja's renewed disappearance disturbing".
It has urged the Pakistan government and the ISI to clarify immediately where they are holding Khawaja and on what charges.
The international human rights group says that "Khawaja should not join the ranks of the disappeared himself".
The Human Rights Commission of Pakistan says 200 people are "missing" who it believes are in the custody of the security agencies.
Many of those released from custody have alleged that they were held by military intelligence agencies.