Pakistan Prime Minister Imran Khan has warned of a bloodbath when India lifts its curfew in disputed Kashmir, saying the conflict could lead to a nuclear war, but India called the threats "brazen and incendiary" and an attempt to justify terrorism.

Key points: Imran Khan said if war broke out between the two countries, Pakistan "will fight"

Imran Khan said if war broke out between the two countries, Pakistan "will fight" India said Pakistan's threat of nuclear war and justification of terrorism was "brazen"

India said Pakistan's threat of nuclear war and justification of terrorism was "brazen" India revoked the special status of Kashmir in August

Mr Khan made the remarks in an impassioned speech to the annual United Nations General Assembly after India last month removed the decades-old autonomy in the part of Kashmir controlled by Pakistan.

"If this goes wrong, you hope for the best but be prepared for the worst," he said.

"If a conventional war starts between the two countries ... anything could happen. But supposing a country seven times smaller than its neighbour is faced with the choice — either you surrender or you fight for your freedom till death?

"What will we do? I ask myself this question … and we will fight. When a nuclear-armed country fights to the end, it will have consequences far beyond the borders."

However, India accused Pakistan of "brinkmanship", saying its threats of unleashing nuclear devastation and justification of terrorism was "brazen and incendiary".

Addressing the United Nations General Assembly, India's Ministry of External Affairs first secretary Vidisha Maitra said Pakistan was "trying to play its wild card as the newfound champion of human rights", while persecuting its own minorities.

"Pakistan is a country that has shrunk the size of its minority community from 23 per cent in 1947 to 3 per cent today," Ms Maitra said.

"[It] has subjected Christians, Sikhs, Ahmadiyas, Hindus, Shias, Pashtuns, Sindhis and Balochis to draconian blasphemy laws, systemic persecution, blatant abuse and forced conversions."

She said India's removal of the "outdated and temporary" Article 370 would integrate Jammu and Kashmir as well as Ladakh with a thriving and vibrant democracy.

In its clampdown in the Indian-controlled part of Kashmir, which has a Muslim majority, India flooded the territory — already one of the world's most militarised zones — with troops.

Protesters rally against India's annexation of Kashmir and occupation of Punjab at a demonstration in New York. ( AP: Mark Lennihan )

It imposed severe restrictions on movements and cut all telephone, mobile phone and internet connections. Thousands of people were arrested.

New Delhi has since eased some of the curbs, although no prominent detainees have been freed and mobile and internet connections remain suspended.

Kashmir has long been a flashpoint between nuclear-armed India and Pakistan. Both countries rule parts of Kashmir while claiming it in full, with China having control over other parts.

Two of the three wars they have fought have been over Kashmir.

Mr Khan addressed the United Nations a day after the senior US diplomat for South Asia called for a lowering of rhetoric between India and Pakistan while saying that Washington hoped to see rapid action by India to lift restrictions it has imposed in Kashmir and the release of detainees there.

ABC/Reuters