An Assam Rifles jawan was killed and four others were injured in a suspected improvised explosive device (IED) blast in Chumoukedima district of Nagaland on Monday, a defence official said.The explosion reportedly targeted an Assam Rifles vehicle during an operational movement, Defence PRO Col Amit Shukla said.Security forces have launched a search operation in the area, while the injured personnel have been shifted for medical treatment.Further investigation is under way, he said.The authorities have not yet released the identity of the victims or confirmed who was responsible for the attack.