Kashmir veteran politician Syed Ali Shah Geelani died on Wednesday night in Srinagar, prompting Indian authorities in the valley to deploy troops around the city and shut down the internet as a precautionary measure, police said.
He was 91 years old.
"Troops are being deployed at sensitive places in Srinagar and other major towns and no vehicular movement is being allowed," a police official said.
Geelani was the most senior leader of the movement to liberate Indian held Kashmir. His family said the elderly politician had been ailing for years and had been under house arrest for the last 12 years after leading several anti-India protests.
A family member told Reuters Geelani developed chest pain and chest congestion on Wednesday afternoon and died late at night at his residence in the region's main city of Srinagar.
Police chief Vijay Kumar told Reuters the internet was shut down down as a precautionary measure and restrictions imposed in the Kashmir valley.
The roads leading to Geelani's residence in Srinagar were sealed, another official said.
Kashmir has long been a flashpoint between India and Pakistan. Tensions between the two countries were renewed, however, after New Delhi withdrew the autonomy of the Indian held region in August 2019 and split it into two federally administered territories.
Last year, Geelani quit his hard line Hurriyat Conference faction, saying that it had failed to counter New Delhi's efforts to tighten its grip on the disputed region.
Hurriyat Conference was formed by various separatist groups in Kashmir in 1993 to provide a political platform for seceding from India in the wake of an armed revolt against New Delhi.
Pakistani Prime Minister Imran Khan expressed grief over Geelani's passing on Twitter and said the nation would observe a day of mourning.
Paying tribute to Geelani, leader of the opposition in the National Assembly Shehbaz Sharif said: "Syed Ali Geelani personified the Kashmir freedom struggle and exposed India's fascist face."
Quoting Pakistan Peoples Party Chairperson Bilawal Bhutto Zardari, the PPP media cell tweeted that he lauded the struggle of Geelani, saying the deceased leader was another name for the liberation movement in Kashmir.
In a tweet, Mushaal Hussein Mullick, Kashmiri leader and wife of Kashmir's Revolutionary Liberation Leader Yasin Malik, said India was threatening the family of the deceased Ali Geelani to bury him within 30 minutes or they would bury him in an unnamed grave away from Srinagar.