Khan gave a forceful rebuke of Prime Minister Narenda Modi's decision Monday to scrap the special status granted to the Indian-ruled part of Kashmir from India's constitution in front of a joint-session of parliament in Islamabad.

"I want to make it clear that we will fight this issue on every forum, (including) at the UN security council," said Khan, who also promised to also raise the issue with heads of state and take the matter to the International Criminal Court.

Khan demanded action from the global community as he accused Modi of blatantly violating international law in pursuit of an anti-Muslim agenda in India.

"If the world does not act today... (if) the developed world does not uphold its own laws, then things will go to a place that we will not be responsible for," Khan added.

The prime minister's remarks came shortly after Pakistan's military announced it "firmly stands" by Kashmiris following a meeting by the army's top commanders in the garrison city of Rawalpindi to discuss the move by India, which is also set to exacerbate the long-running bloody rebellion in Kashmir.

"Pakistan Army firmly stands by the Kashmiris in their just struggle to the very end. We are prepared and shall go to any extent to fulfil our obligations in this regard," General Qamar Javed Bajwa said, in a tweet sent by a military spokesman after the meeting.

Spokesman Major General Asif Ghafoor said commanders "fully supported" the civilian government's rejection of India's move.

"Pakistan never recognised the sham Indian efforts to legalise its occupation" of the disputed mountainous region, he added.

On Tuesday, an estimated 500 people demonstrated in Muzaffarabad, the largest city in Pakistani-held Kashmir, with more protests expected in major cities across the country.

Pakistani lawmakers also began a session of parliament to discuss a possible response to Delhi's move.

The breathtaking Himalayan region of Kashmir has been disputed by India and Pakistan since independence in 1947. They have fought two of their three wars over the former principality.

Earlier this year they came close to war yet again, after a militant attack in Indian-held Kashmir in February was claimed by a group based in Pakistan, igniting tit-for-tat air strikes.

For three decades the Indian-administered part has been in the grip of an insurgency that has left tens of thousands dead.

Armed Kashmiri rebels and many residents have fought for the Muslim majority region's independence or to join neighbour Pakistan.

Ahead of the announcements, tens of thousands of extra Indian troops were deployed in the territory, and a security lockdown was imposed overnight Sunday. All telecommunications have been cut there since.

Editorials and social media in Pakistan were buzzing Tuesday over Modi's decision, with the English daily Dawn running a large headline on its front page reading: "New Delhi sheds fig leaf, robs held Kashmir of special status".