India's counter-terrorism agency has arrested a prominent Kashmiri human rights activist under a draconian anti-terrorism law which makes it nearly impossible to get bail.
Khurram Parvez has been accused of "terror-funding" and "conspiracy".
The National Investigation Agency (NIA) arrested him after raids at his home and office in Indian-administered Kashmir. Mr Parvez is yet to comment.
But the arrest has caused global outrage amid calls for his release.
Activists and others on social media have called the arrest an attempt to "silence and punish human rights defenders".
Mr Parvez has long been a vocal critic of the ruling Bharatiya Janata Party (BJP)-led government. His Jammu Kashmir Coalition of Civil Society (JKCCS), a group based in Kashmir, has published several scathing reports on human rights violations and excesses committed by security forces in the Valley.
He is also the chairperson of the Asian Federation Against Involuntary Disappearances (Afad), an international rights organisation which looks into the forced disappearances in Kashmir and elsewhere in Asia.
In 2016, Indian authorities had arrested Mr Parvez a day after he was barred from travelling to Switzerland to attend the 33rd session of United Nations Human Rights Council, and had charged him under the controversial Public Safety Act (PSA), which allows detention without charge for up to two years.
He was released after 76 days in prison after increased pressure from international rights groups.
On Monday, investigators from the NIA searched his home and the office of JKCCS in Srinagar, Kashmir's main city. He was initially taken for questioning and was arrested later in the evening.
The police have charged him under various sections of the draconian Unlawful Activities (Prevention) Act, including "criminal conspiracy", "attempt to wage war against the government" and for "raising funds for terrorist acts and a terrorist organisation".
The United Nations' Special Rapporteur on Human Rights Defenders, Mary Lawlor, said she was disturbed to hear about Mr Parvez's arrest. "He is not a terrorist, he is a human rights defender," she wrote on Twitter.
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The arrest also comes at a time when tensions are boiling over in the Kashmir valley after the recent death of two civilians.
Police said the men were allegedly killed in crossfire when security forces attacked suspected militants in Srinagar. But families of the civilians have denied the police version of events, saying they were deliberately killed by Indian troops while being used as a human shield.
The deaths sparked days of protests in the region, which has seen an insurgency against Indian rule since 1989.
Both India and Pakistan claim the territory in its entirety but control only parts of the region. The nuclear-armed neighbours have gone to war twice over it.
For years, India has accused Pakistan of pushing thousands of militants across the border to foment instability in Indian-administered Kashmir. Islamabad denies the charge.