Veteran Kashmiri separatist leader and former chairman of All Parties Hurriyat Conference (APHC) Syed Ali Shah Geelani passed away at his Srinagar residence on Wednesday, APHC leader Abdul Hameed Lone said.
Geelani was battling severe lung ailments and dementia.
According to the Kashmir Media Service, the veteran Kashmiri leader was 92.
Security has been strengthened in the occupied Kashmir Valley following his death.
Geelani was active in the political landscape of the Illegally Indian Occupied Jammu and Kashmir for around five decades.
Last year, Geelani resigned from his post as APHC chief. He was elected the party's chairman for life in 2003.
Hurriyat Conference (Geelani) has more than 24 constituent parties, some of which have only a handful of members.
Meanwhile, Prime Minister Imran Khan expressed grief over the death of Geelani.
"Deeply saddened to learn of the passing of Kashmiri freedom fighter Syed Ali Geelani who struggled all his life for his people and their right to self-determination. He suffered incarceration & torture by the Occupying Indian state but remained resolute," PM Khan said in a Twitter message.
"The Pakistan flag will fly at half-mast and we will observe a day of official mourning," the premier announced.