Manipur Chief Minister Okram Ibobi Singh said that Monday’s bomb blast at Sangakpham in Imphal, is a handiwork of the National Socialist Council of Nagaland-Isaac Muivah (NSCN-IM).Giving details of the police investigation into Monday ‘s explosion, the Chief Minister told media persons this evening at Imphal that the main culprit of the blast was among those five killed in the incident.The Chief Minister also said that the outfit has been directly responsible for at least six major violent incidents in Manipur in the recent past including the ambush on the car-cade of state MLA Wungnaoshang Keishing on April 15 last.Mr. Ibobi Singh said that state government is seriously considering to take up the matter with Central Government as the outfit is holding talks with the centre for more than 10 years.