- Pakistani activist Asma Jahangir died of cardiac arrest
- Pakistan Prime Minister Shahid Khaqan Abbasi expressed grief at her death
- Asma Jahangir was an outspoken critic of the Pakistan army
The lawyer and former UN special rapporteur died of cardiac arrest, according to her sister.
"Unfortunately we have lost her," Hina Jilani, also a prominent rights activist and lawyer, told AFP.
Funeral arrangements have yet to be announced, according to a statement by her daughter Munizae Jahangir, as the family waited for relatives to return to their hometown of Lahore.
Prime Minister Shahid Khaqan Abbasi expressed grief at Asma Jahangir's death, praising her contribution to upholding the rule of law and safeguarding human rights.
Ms Jahangir's supporters and former opponents alike took to social media to offer their condolences and express shock at news of her death.
"Asma Jahangir was the bravest human being I ever knew. Without her the world is less," wrote prominent Pakistani lawyer Salman Akram Raja.
In 2014 Asma Jahangir received France's highest civilian award and Sweden's Right Livelihood Award, for her decades of rights work.
Few Pakistani rights activists have achieved the credibility of Ms Jahangir.She braved death threats, beatings and imprisonment to win landmark human rights cases while standing up to dictators.
Ms Jahangir also helped establish the Human Rights Commission of Pakistan.
The organisation made its name defending religious minorities and taking on highly charged blasphemy accusations along with "honour" killings -- in which the victims, normally women, are murdered by a relative for bringing shame on the family.
"There was a time that human rights was not even an issue in this country. Then prisoners' rights became an issue," she said.
"Women's rights was thought of as a Western concept. Now people do talk about women's rights -- political parties talk about it, even religious parties talk about it."
Asma Jahangir secured a number of victories during her life, from winning freedom for bonded labourers from their "owners" through pioneering litigation, to a landmark court case that allowed women to marry of their own volition.
She was also an outspoken critic of the powerful military establishment, including during her stint as the first-ever female leader of Pakistan's top bar association.
Ms Jahangir was arrested in 2007 by the government of then-military ruler Pervez Musharraf. In 2012 she claimed her life was in danger from the feared Inter Services Intelligence spy agency.