In anticipation of the announcement, which many analysts predicted could set off rioting and unrest, India had flooded Kashmir with thousands of extra troops. The Indian authorities also evacuated tourists, closed schools and cut off internet service.
For many years, Kashmir has been governed differently than other parts of India, and the government’s decision to revoke parts of Article 370 of the Constitution is widely seen as a blow to Kashmir’s special status. India’s governing Bharatiya Janata Party, known as the B.J.P., has deep roots in a Hindu nationalist ideology and one of its campaign promises during the election this year had been removing the special status of Kashmir, which is predominantly Muslim.
“Today the B.J.P. has murdered the Constitution of India,” said Ghulam Nabi Azad, a senior leader of the Indian National Congress, an opposition party.
The Indian government also said that it would support a parliamentary bill to split the state of Jammu and Kashmir, which includes the Kashmir Valley, into two federal territories: Jammu and Kashmir, which will have a state legislature, and Ladakh, a remote, high-altitude territory, which will be without a legislature.
Amit Shah, the home minister, said the government had the legal authority to change Kashmir’s status. But some analysts said that was not so clear and that the issue would most likely end up before India’s Supreme Court.
A sense of panic has spread across Kashmir as millions of residents woke up Monday to deserted streets. Relatives of Kashmiris who could be reached by phone said that many people were fearful about stepping outside and were waiting in their homes for news about what was going to happen next.
Many Kashmiris had feared that the Indian government, led by Prime Minister Narendra Modi, would either remove their region’s special status or turn Kashmir into a federally ruled territory.
Separatist groups, including some that are armed and maintain links to neighboring Pakistan, have been chafing for independence from India for years. Analysts say that any steps that reduce Kashmir’s autonomy could demoralize the Kashmir public further and provoke an outburst of serious violence.
The Pakistani Foreign Ministry condemned the Indian announcement as a violation of United Nations resolutions, saying in a statement on Monday that “Pakistan will exercise all possible options to counter the illegal steps.”
Politicians across the political spectrum urged the Pakistani government to come up with a strong, swift and effective diplomatic response.
Shahbaz Sharif, president of the Pakistan Muslim League-Nawaz political party, said that Pakistan should call for an emergency meeting of the United Nations Security Council.
“The people of Kashmir cannot be left alone at this moment,” he said. “We will go to every extent to defend the human rights and legal rights of Kashmiris.”
Mr. Sharif added, “Kashmir is the jugular vein of Pakistan, and anyone laying a hand on our jugular vein and honor will meet a frightful end.”
Before the Indian announcement, as anxiety was building in Kashmir, Prime Minister Imran Khan of Pakistan said that the only road to lasting peace in South Asia ran through the region.
In a Twitter post on Sunday, Mr. Khan said that President Trump had offered to mediate the Kashmir dispute when the two leaders met in Washington last month.
“This is the time to do so as situation deteriorates there and along the LOC with new aggressive actions being taken by Indian occupation forces,” Mr. Khan wrote, referring to the Line of Control, the name of the disputed border between Pakistan and India. “This has the potential to blow up into a regional crisis.”
Over the last few days, the authorities in Kashmir had been issuing satellite phones to senior police officers so they could communicate in case the cellphone network was disrupted, which happened around midnight going into Monday, according to widespread news reports.
The authorities have also restricted the movements of prominent Kashmiri political leaders, including Omar Abdullah and Mehbooba Mufti, according to many reports in the Indian news media.
Ms. Mufti, the most recent chief minister of Jammu and Kashmir, said in an interview before Mr. Shah’s announcement on Monday that Kashmiri politicians were coming together to defend against any possible moves by India to remove the special laws that grant limited autonomy to Kashmir under the Indian Constitution.
“There will be chaos if our identity is compromised,” Ms. Mufti said. “We will go to any extent to preserve that identity guaranteed under the India Constitution.”
Security officers have evacuated thousands of tourists, mostly Indians, telling them it was dangerous to be in the valley and that militant groups might be planning an attack.
Janvi Singh, an entrepreneur from Mumbai, saw her vacation suddenly cut short.
She had just arrived at her hotel in Gulmarg, a scenic mountainside town, on Friday when government officials knocked on the door of her room and told her she needed to leave immediately.
“They didn’t take no for an answer,” Ms. Singh said.
For decades, Kashmir has been plagued by turmoil. When India and Pakistan won independence from Britain in 1947, Kashmir originally opted to remain a small independent state.
But militants from Pakistan soon invaded Kashmir, leading it to seek protection from India. Kashmir agreed to become part of India only under certain conditions that guaranteed its autonomy, which were protected by Article 370. India and Pakistan then fought several wars over the area and today most of Kashmir is administered by India, with a smaller slice controlled by Pakistan, which like Kashmir is majority Muslim.
Tensions reached a breaking point in February, when a Kashmiri militant rammed a vehicle filled with explosives into a convoy of Indian paramilitary forces traveling on a highway, killing at least 40 soldiers. A banned terrorist group, Jaish-e-Muhammad, which is based in Pakistan, claimed responsibility.
It was the worst attack in the region in three decades, and set off a tense military standoff between India and Pakistan that culminated in a dogfight between Indian and Pakistani warplanes. Pakistan shot down and captured an Indian pilot, who was soon handed back to India.
Over the last year, activists say, the hunt for separatists has intensified, pulling ordinary Kashmiris into the fold.
Indian Army officials said Friday that they had specific information about a planned attack by Pakistan-based militants on Hindu pilgrims and tourists.
But many Kashmiris were skeptical of those claims and wondered if there was another explanation for the sudden troop buildup in the region, already one of the most heavily militarized areas in the world.
Many residents are now panicking. People are hoarding supplies, causing shortages of medicine and baby food. Many fuel stations ran dry as thousands of people lined up through Friday and Saturday nights to fill their cars with gas.
“All the hotels in Gulmarg are empty,” said Muzamil Ahmad, director of an upscale hotel there.
Germany, one of the few Western countries that had earlier removed restrictions on travel to the region, issued a travel advisory asking its citizens to avoid the valley. Britain, Australia and Israel issued similar warnings.
Along the Line of Control, both sides have been building up their troop levels.
On Saturday, Pakistani officials accused India of using cluster bombs along the border that killed two civilians and wounded 11 on the Pakistan side. India denied it used cluster bombs, which have been criticized across the world as being dangerous to civilians.