Naga insurgent group National Socialist Council of Nagaland (Isak-Muivah) on Thursday called for “third-party intervention” in its talks with the Centre, failing which it threatened to resume “violent armed resistance” against the government.

Thiungaleng Muivah, the general secretary of the insurgent group, accused the Centre of betraying the letter and spirit of a Framework Agreement that it signed on August 3, 2015. This came after the Centre refused to recognise a separate Naga flag and Naga constitution, which was a key demand of the National Socialist Council of Nagaland (Isak-Muivah), or the NSCN-IM.

“In order to conclude and realise an honourable political agreement, we rule out peaceful means against the ignominious betrayal of the letter and spirit of the Framework Agreement of August 3, 2015 by the Government of India,” the insurgent group said.

It added that if the Centre rejected the proposal for third-party intervention, it would “resume the violent armed resistance against India for defending Nagalim unique history and her sovereign existence”.

Several Naga groups, including the NSCN-IM, claim that the Nagas neither agreed to be part of the Indian union, nor accepted the Indian Constitution. The NSCN-IM is among the oldest such groups and had been engaged in a conflict with security forces for several decades.

The Indian government signed a ceasefire agreement with the NSCN-IM in 1997.

There was, however, little headway until 2015, when the Centre signed the Framework Agreement with the group – a development publicised as a major breakthrough by both sides.

Following this, conflicting claims about the agreement have led to a deadlock in the peace talks between the group and the Centre, including over the demand for a Naga flag and a separate Constitution.

The NSCN-IM also claimed that the Centre had agreed to recognise the “unique history” of the Nagas and the concept of “shared sovereignty”. However, the Centre rejected the claims and said that the group had misinterpreted the 2015 agreement.