Over four months after the NSCN-K carried out an ambush in Manipur that left 18 security personnel dead, the Centre on Wednesday declared the outfit as an unlawful organisation for a period of five years.

"The government today (Wednesday) decided to declare National Socialist Council of Nagaland (Khaplang) (NSCN-K) as an unlawful organisation for a period of five years, under the Unlawful Activities (Prevention), Act 1967," the home ministry said in a statement.

"The decision was taken considering the continued hostility and violence on part of the NSCN-K against the Indian security personnel, from their bases in Myanmar," it added.

The NSCN-K abrogated a ceasefire entered into with the Indian government in 2001 with a series of incidents begining from March 2015.

The ban comes after the central government signed a framework peace agreement with the NSCN's Isak-Muivah faction on August 3 and a ceasefire agreement with the newly formed Reformation faction under Wangtin Naga on April 27.

After the NSCN-IM entered into a ceasefire agreement with the Indian government in 1997, NSCN-K led by Shangwang Shangyungi Khaplang followed suit in 2001.

At the alleged instigation of United Liberation Front of Asom-Independent (ULFA-I) leader Paresh Baruah, the NSCN-K carried out a shootout in Nagaland's Kohima on March 26 and a bomb blast in Wokha on March 27.

Following this, two close aides of Khaplang, Wangtin Naga and P. Tikhaka, who had come to Dimapur for peace negotiations with the Indian authorities, expressed surprise at the ceasefire abrogation by their group and formed another faction called the NSCN-Reformation and entered into a ceasefire agreement with the Centre.

According to Wednesday's home ministry statement, the NSCN-K has carried out a series of violent attacks on the Indian armed forces from their bases in Myanmar.

Apart from the March attacks, it carried out two improvised explosive device (IED) explosions on April 15 and 16 at Lerie Colony, near CRPF Camp on the National Highway 29 in Kohima district of Nagaland.

"Ambush of a party of security force personnel at village Changlang Shu, under Tobu police station of district Mon (in Nagaland), killing eight security forces personnel," the home ministry statement cited as another reason.

The final straw was an ambush the NSCN-K carried out on June 4 in Chandel district of Manipur, that left 18 security personnel dead.

The home ministry's statement on Wednesday comes a week after the National Investigation Agency declared Rs.700,000 and Rs.100,000 rewards for the arrest of S.S. Khaplang and another NSCN-K militant, Niki Sumi.