In a fiery speech lasting 50 minutes, Khan said India could unleash a "bloodbath" in the Muslim-majority territory, as the nuclear-armed rivals took center stage at the UN General Assembly.

His heated rhetoric stood in stark contrast to Indian Prime Minister Narendra Modi's address an hour earlier, when the Hindu nationalist leader touted domestic successes but made only an oblique reference to terrorism, taken to mean Pakistan.

The speeches occurred as thousands of protesters gathered outside the UN building to demonstrate, both in support of Modi and against the clampdown in Kashmir, which has been under lockdown since New Delhi scrapped its semi-autonomous status in early August.

Khan warned there could be a repeat of the fighting between the regional rivals seen in February if India blamed his country for a homegrown militant attack in response to the crackdown.

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

"What will we do? I ask myself these questions. We will fight ... and when a nuclear-armed country fights to the end, it will have consequences far beyond the borders," warned Khan, whose speech was punctuated by applause, mainly by the Pakistani delegation but at times others.

- 'Bloodbath' -

The 66-year-old Pakistani leader also accused Indian forces of preparing for a genocide once the curfew was eventually lifted.

"There are 900,000 troops there, they haven't come to, as Narendra Modi says -- for the prosperity of Kashmir," Khan said. "These 900,000 troops, what are they going to do? When they come out?

"There will be a bloodbath," Khan said.

India has not stated the number of troops in Kashmir, but Khan's 900,000 figure would be the equivalent of two-thirds of the Indian army.

India accuses Pakistan of arming, funding and training militants in Kashmir and says it has taken action to preserve calm.

"Free Kashmir, End the Siege," read banners during the pro-Pakistan demonstration, while on the pro-Modi side protesters held up placards hailing the Indian leader as a "visionary" and saying, "Pakistan, what about your minorities?"

Rozeena Khan, a teacher originally from Indian Kashmir, said she could not speak to her 86-year-old father and was concerned for his welfare.

"Kashmir is a prison, the world's largest prison right now," she said.

"I feel like my brain, my heart, is with my family there. I should concentrate on my job but I will tell you honestly, sometimes when I think, I cry at my job, I cry."

Security forces in Srinagar, the summer capital of India's former Jammu and Kashmir state, imposed tough new restrictions on Friday, fearing protests surrounding the twin speeches in New York.

They erected concrete and razor-wire barricades as troops in bulletproof gear guarded deserted streets following orders to stop any public rallies.

- 'I would pick up a gun' -

Khan said that the conditions in Kashmir were radicalizing a new generation and that he himself would take up arms in their situation.

"I've been locked up for 55 days, I've heard about rapes, Indian army going in homes," he said, imagining himself as a Kashmiri.

"Would I want to live this humiliation? Would I want to live like that? I would pick up a gun. You're forcing people. You are forcing people into radicalization."

Stephane Dujarric, the UN chief's spokesman, later told reporters Antonio Guterres had raised his concerns over Kashmir both publicly and privately and favored dialogue.

"He of course remains very concerned about any potential escalation between Pakistan and India over the situation in Kashmir," Dujarric said.

Alice Wells, the top US State Department official for South Asia, on Thursday said that Washington is pressing New Delhi to quickly ease its restrictions in Kashmir, while also calling on Khan to dial down his rhetoric.

India has long resisted efforts to internationalize Kashmir and Modi did not mention it in his speech.

The Indian leader instead chose to focus on domestic policies such improving access to toilets and helping millions open bank accounts.

He did, however, make a veiled reference to Pakistan, telling fellow leaders: "We belong to a country that has given the world, not war, but Buddha's message of peace.

"And that is the reason why our voice against terrorism, to alert the world about this evil rings with seriousness and outrage."