Indian security forces have arrested more than 500 people since New Delhi imposed a communications blackout and security clampdown in divided Kashmir, where people remained holed up in their homes for the fourth day.
Pakistan, which claims the divided Himalayan region together with India, on Thursday suspended a key train service with India over a change in Kashmir's special status by New Delhi, as tensions between the rivals soared.
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India's government this week revoked the special status of Jammu and Kashmir and downgraded the region from statehood to a territory. Rebels in Muslim-majority Kashmir have been fighting Indian rule in the portion it administers for decades.
State-run All India Radio, which reported on the arrests without details, also said that cross-border firing by Indian and Pakistani troops hit the Rajouri sector of the Indian-controlled Kashmir late on Wednesday.
In response to India's action, Pakistan's Federal Minister for Railways Sheikh Rashid Ahmad suspended the Express, or Friendship Express, train service to India starting on Thursday.
Islamabad on Wednesday said it would downgrade its diplomatic ties with New Delhi, expel the Indian ambassador and suspend trade. Prime Minister Imran Khan told Pakistan's National Security Committee that his government will use all diplomatic channels "to expose the brutal Indian racist regime" and human rights violations in Kashmir, the government's statement said.
India regretted Pakistan's steps and said in a statement that "the intention behind these measures is obviously to present an alarming picture to the world of our bilateral ties."
The External Affairs Ministry said it was not surprising that Pakistan has negatively perceived India's decision to end Kashmir's special status as Islamabad "has used such sentiments to justify its cross-border terrorism".
Describing India's latest steps in Kashmir as internal affairs, the statement urged Pakistan to review its decision to downgrade ties so that normal channels for diplomatic communications are preserved.
An uneasy calm prevailed along the Line of Control where Pakistani troops face off Indian forces in Kashmir. People living in border villages were awaiting government instruction to move to safer places, although some residents had already moved to nearby towns.
India and Pakistan have fought two of their three wars over control of Kashmir. The first war ended in 1948 with a UN-brokered ceasefire that left Kashmir divided and promised its people a UN-sponsored referendum on the region's future.
Pakistan said it would ask the United Nations to pressure India to reverse its decision to downgrade Kashmir from a state to two separate territories. The region also lost its right to fly its own flag and make many of its own decisions.
On Thursday, Indian authorities in Kargil district of the Leh region, which used to be part of Jammu and Kashmir state, banned the assembly of more than five people at one place to prevent protests against the division of Kashmir into two union territories.
The decision came after religious and political organisations in Kargil condemned the Indian government decision and held a district-wide shutdown on Tuesday.
Kashmir is India's only Muslim-majority state and most people oppose Indian rule. The insurgency that began in 1989 and India's ensuing crackdown have killed more than 70,000 people.