Fifteen persons, including one civilian, were killed in the worst-ever incident involving two factions of the National Socialist Council of Nagaland. An irate mob also ransacked and set on fire the ceasefire monitoring office of NSCN(IM) on the outskirts of Dimapur in Nagaland on Friday.It all began on Friday morning when a group of NSCN(Unification) cadres were allegedly ambushed by the rival NSCN(IM) near Seithekima-C village, about 15 km from Dimapur town, leading to the death of 12 of them on the spot. By evening, the casualties went up to 15, an Army spokesman said.While the police rushed to the spot and recovered 12 bodies, an irate mob of over 3,000 people blocked the National Highway 39, that links Dimapur to Kohima, and raised slogans against NSCN(IM) and its leader Thuingaleng Muivah. Sources at Dimapur said as the bodies of the 12 persons arrived in the town for postmortem examination, and even as the national highway remained blocked, the agitated mob marched to NSCN(IM)’s ceasefire monitoring office in Diphupar and set it ablaze. A group of NSCN(IM) cadres, who were reportedly in the office, opened fire on the mob, leading to the death of a civilian. The incident occurred around noon, official sources said. The mob also prevented IRB jawans and the police from entering Diphupar.Friday’s incident occurred on a day when Naga National Council, the original Naga separatist group that A Z Phizo had started in the 1940s, asked the people of Nagaland to observe the 58th anniversary of the plebiscite it organised that had rejected the very concept of remaining a part of India.It was only on Wednesday that Union Home Minister Shivraj Patil had visited Nagaland along with several Home Ministry officials to review the law and order situation in the backdrop of increasing violence between the NSCN factions. While Patil assured Chief Minister Neiphui Rio of all possible help from the Centre to contain law and order, he also urged the state Government to rein in militants.An Army spokesman in Kohima said rivalry between the two factions had increased since November last year when Azheto Chophi, ‘kilo kilonser’ (home minister) of the NSCN(M)’s underground ‘government of the people’s republic of Nagalim’ had quit the group to float NSCN(U). While Chophy took with him 27 cadres, the NSCN(U) began moving closer to NSCN(K).The authorities have been in a fix in tackling NSCN(U), because there is no ceasefire with it, as exists between the Union Government and the two factions, NSCN(IM) and NSCN(K).