The Indian government on Monday rushed through a presidential decree to scrap a special status for disputed Kashmir, hours after imposing a major security clampdown in the region.
Home Minister Amit Shah told parliament that the president had signed a decree abolishing Article 370 of the constitution giving special autonomy to the Muslim-majority Himalayan region.
The decree said the measure came into force "at once."
Pakistan on Monday condemned and rejected the Indian government decision to scrap the special status.
"Pakistan strongly condemns and rejects the announcements made by the Indian Government regarding the Indian Occupied Jammu & Kashmir," Mohammad Faisal, Foreign Ministry spokesman, said in a statement.
"No unilateral step by the government of India can change this disputed status, as enshrined in the United Nations Security Council (UNSC) resolutions. Nor will this ever be acceptable to the people of Jammu & Kashmir and Pakistan," Faisal said.
Pakistan will exercise all possible options to counter the illegal steps, he added.
Foreign Minister Shah Mahmood Qureshi, in a series of tweet, said that Islamabad would "firmly highlight" its stance on the Kashmir issue in their "meetings with the U.S. delegation visiting Pakistan and with the International Community at large."
"Pakistan reaffirms it's abiding commitment to the Kashmir cause and its political, diplomatic and moral support to the people of Occupied Jammu and Kashmir for realization of their inalienable right to self-determination," he added.
The measure also means 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.
The law had also reserved state government jobs for residents, as well as college places, in an effort to keep the state from being overrun by people from the rest of India.
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.
Political leaders in Kashmir had warned that repeal of the law would trigger widespread unrest.
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.
Monday's announcement came hours after authorities launched a clampdown in Kashmir by suspending telephone services and placing state leaders under house arrest.
Telephone and internet services were suspended early on Monday, and state leaders wrote on Twitter that they had been put under house arrest.
On Sunday, a meeting of regional parties had vowed to safeguard the region's special status, saying any move to scrap the privilege would amount to aggression against the people of the state.
Tension had risen since Friday, when Indian officials issued an alert over possible militant attacks by Pakistan-based groups.
Pakistan has rejected those assertions, but thousands of alarmed Indian tourists, pilgrims and workers streamed out of the region over the weekend.