A leader of the insurgent group NSCN(IM) who was suspected to be involved in the killing of a lawmaker from Arunachal Pradesh in May was arrested at a remote village in Assam, near the border with Nagaland.
In a joint operation, personnel of the Army, its adjunct Assam Rifles and the state police spread out across Longding-Charaideo-Mon region, 500 km from Guwahati, and laid an ambush on the suspected routes used by NSCN(IM) insurgents on Sunday around 2 am.
At 3:30 am, one of the teams stopped a vehicle that was passing through the area, and on checking, they found the insurgent Anok Wangsa along with guns and ammunition concealed in the vehicle, the Army said.
"The individual confirmed that he had hidden more weapons, ammunition and war like stores in his house located on Assam-Nagaland border. The teams then carried out a detailed search of his house which resulted in recovery of large cache of arms," the Army said in a statement.
Anok Wangsa is the aide of Absolom Tangkhul, another leader of the NSCN(IM), who has been accused of killing Arunachal Pradesh lawmaker Tirong Aboh, his son and nine others in an ambush in May when the national election was going on.
Mr Aboh, 45, was shot dead while he was on his way to from Assam's Dibrugarh to his constituency, Khonsa West, from where he was seeking re-election to the state assembly.
The National Socialist Council of Nagaland (Isak-Muivah), the largest insurgency group in the north-east, has a ceasefire with the centre and it has to report the location of all its camps to the Army.
Earlier this month, the Army dismantled an undesignated hideout of the insurgent group in Manipur after its members were found extorting from people at a village.
The NSCN (IM), formed in 1980, is led by 85-year-old Thuingaleng Muivah; the other top leader of the group, Isak Chishi Swu, died three years ago at 87 of multi-organ failure.
Over the years, the NSCN-IM has been accused of killings, extortion and other subversive activities and its persistent demand for separation from India led to a military clampdown on the group.
In 1997, the NSCN-IM entered into a truce with the central government for peace and since then has been continuing dialogue with the centre's emissaries.
In August 2015, the NSCN-IM signed a framework agreement with the government which Prime Minister Narendra Modi described as a "historic" step to usher in peace in the state.
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