India's government on Monday announced plans to revoke the special status of Kashmir, hours after authorities launched a clampdown in its only Muslim-majority region.
Interior Minister Amit Shah told parliament the government would scrap a constitutional provision that grants special status for disputed Kashmir and allows the state to make its own laws.
"The entire constitution will be applicable to Jammu and Kashmir state," Shah said.
In a subsequent order, India's president approved the government's changes.
The step would also mean revocation of a bar on property purchases by people from outside the state. Such plans have in the past provoked warnings of a backlash in Kashmir, which is claimed by both India and Pakistan.
Prime Minister Narendra Modi's ruling party had pushed for an end to Kashmir's special constitutional status, arguing that such laws had hindered its integration with the rest of India.
India's decision led to widespread protests across Pakistan. The government said it strongly condemned India's constitutional changes in Kashmir.
Since last year, Kashmir has been ruled by the Indian federal government, after Modi's Hindu nationalist Bharatiya Janata Party (BJP) withdrew from a coalition there with a regional party.
Kashmir in lockdown
Monday's announcement came hours after authorities suspended telephone services and placed state leaders under house arrest.
The clampdown began in the early hours of Monday when Indian authorities said they were imposing restrictions on public movement and shutting all educational institutions in the main Srinagar city.
Some regional leaders around midnight tweeted saying they have been or feared being arrested.
Omar Abdullah, a former chief minister of the state, said he believed he was being placed under house arrest, appealing to people to stay calm.
Mehbooba Mufti, another ex-chief minister and Modi's former ally, said it was "ironic that elected representatives like us who fought for peace are under house arrest."
A spokesman for India's federal home ministry in New Delhi did not respond to a request for comment.
"To place two former Chief Ministers under house arrest is unprecedented and unacceptable. Would it happen in any other state of India? Is this how we build trust among the Kashmiris?" prominent historian and columnist Ramachandra Guha said on Twitter.
Protests in Pakistan
India's decision to revoke Kashmir's special status led to protests all over Pakistan. In Muzaffarabad, the capital of Pakistan-administered Kashmir around 45 kilometres from the contested border, protesters held black flags and burn car tyres while chanting "Down with India."
There were also protests in Islamabad, Pakistan's capital, and Karachi, the country's commercial hub.
India's decision is 'illegal' says Pakistan
Pakistan's foreign ministry said in a statement it would "exercise all possible options to counter the illegal steps," taken by India.
Foreign Minister Shah Mahmood Qureshi said it would raise the issue with allies, including the United States.
"We intend to firmly highlight our stance in our meetings with the US delegation visiting Pakistan and with the international community at large," Qureshi said on Twitter.
India's foreign ministry has not replied to Pakistan's statement that the action was illegal.
Pakistan's Prime Minister Imran Khan has not given a statement either. Analysts believe he is likely to avoid escalating tensions with India for now.
Tensions in Kashmir, claimed by both India and Pakistan, have risen since Friday when local Indian officials issued an alert over possible militant attacks by Pakistan-based groups.
Pakistan has rejected those assertions, but thousands of Indian tourists, pilgrims and workers left the region in a panic over the weekend.
Indian authorities also issued a notice for Srinagar city saying there "shall be no movement of (the) public and all educational institutions shall also remain closed" until further orders.
High tension ground
Tensions between the two countries have been running high since February when a militant group based in Pakistan attacked an Indian paramilitary convoy in Kashmir, killing at least 40 people.
For a long time, India has accused Pakistan of fomenting a decades-long armed insurrection against its rule in the portion of Kashmir it controls, which Islamabad denies.