Camp Hebron, Nagaland    -   Thuingaleng Muivah, leader of India’s oldest rebel organisation, has told Al Jazeera that he felt the Indian government’s abrupt decision to strip Kashmir’s special status was “unacceptable”.

The 85-year-old leads the National Socialist Council of Nagalim - Isak Muivah (NSCN-IM) - northeast India’s largest rebel outfit with an estimated 5,000 to 15,000 members fighting for independence for more than four decades.

NSCN-IM, formed in 1980, along with other armed groups based in Nagaland - a Christian-majority state - wants all Naga people unified in a new sovereign state called Nagalim. But the August 5 decision by the Indian government to scrap Article 370 of the constitution that granted Indian-occupied Kashmir a measure of autonomy has triggered anxieties across the northeast region.

Nagaland is safeguarded by Article 371A, which exempts it from following Indian laws. Seven northeast states, including parts of Assam state, are protected under various clauses of Article 371.

“India’s Kashmir decision [was taken] without respecting the history of the Kashmiris. [It] is not acceptable to us,” he said.

Expressing disappointment with the way the Modi government diluted Kashmir’s special status, Muivah said he feels “nothing short of betrayal” since India removed Kashmir’s special status and brought its only Muslim-majority region under direct central rule.

Although India’s hardline Home Minister Amit Shah has reassured regional leaders in the northeast that Article 371 will not be scrapped, rebel groups fear that the current BJP government may dilute these constitutional provisions as part of its “one nation one constitution” vision.

NSCN-IM, which signed a ceasefire deal in 1997, wants Nagalim to include all Naga-majority areas straddling across Manipur, Assam and Arunachal Pradesh states, as well as a part of western Myanmar across the border.

In 2015, the rebel group led by Muivah signed a 16-point framework agreement with Prime Minister Modi and interlocutor RN Ravi but talks aimed at arriving at a political solution has dragged on.

Muivah, who is based at Camp Hebron, the headquarters of the self-styled Government of the People’s Republic of Nagalim, has expressed concerns at talks.

Speaking from the camp spread across 200 acres in Peren district of Nagaland, he said the Indian government was backtracking on the question of Nagaland’s sovereignty, a separate constitution for the state and a flag for the Nagas. “Suddenly, they want the Nagas to come within the union of India. This came as a surprise to us,” he told Al Jazeera. “Sorry, but that is not possible.”

In 1980, the NSCN-IM broke away from the first armed group formed in the 1960s, the Naga National Council, after a group of leaders signed the Shillong Accord in 1975, accepting the constitution of India, without condition.

While no definitive figures are available, the armed rebellion has cost lives running up to thousands, including civilians and Indian armed forces personnel. Since the framework agreement was signed, speculations have been rife over the kind of Naga sovereignty being negotiated.