A police spokesman told IANS that Khurram Parvez is "under preventive custody and that he was being interrogated".
Parvez, 39, is the programme coordinator with the Jammu Kashmir Coalition of Civil Society (JKCCS). He has been an active rights activist for nearly 15 years.
He is also the chairperson of the Asian Federation Against Involuntary Disappearances (AFAD) -- a Manila based conglomerate of rights groups.
Parvez's family alleged that he was picked up from his home in the upscale Gupkar neighbourhood after a midnight raid. They alleged that policemen who took him carried no warrant and gave no reason for his detention.
His detention comes two days after he was stopped at the Delhi airport from boarding a flight to Geneva where he was to the attend a session of the United Nations Human Rights Council (UNHRC).
Parvez had planned to submit a report to the rights council on the situation in the Kashmir Valley, which has seen some 88 deaths in over two months of civilian unrest, triggered by the July 8 killing of Hizbul Mujahideen commander Burhan Wani.
The alleged unlawful detention of the activist sparked off widespread condemnation.
Global rights group Amnesty International's India chapter called for his "immediate release unless he is charged with recognizable criminal offences".
"Preventing a well known activist from travelling abroad for human rights advocacy, and then locking him up on spurious grounds, is a shameful attempt to suppress a peaceful dissenting voice from Kashmir," Aakar Patel, Executive Director at Amnesty International India, said in a statement.
An AFAD statement said the "procedures followed for Parvez's arrest clearly violate" international laws on civil and political rights.
"Such blatant violation is aggravated by the fact that he has not yet been granted access to a lawyer. The arrest is part of the government's strategy to repress and silence human rights defenders in Jammu and Kashmir."
JKCCS in a statement said the "detention of Parvez and denial of his right to lawyers represent a real and imminent security threat that requires urgent attention and action".
