A Border Security Force (BSF) trooper was killed and three civilians injured on Saturday in Jammu and Kashmir's Kupwara district as Pakistan troops again violated the LoC ceasefire, police said.Police said Pakistan army resorted to unprovoked firing at Indian positions in Keran sector of the Line of Control (LoC) in Kupwara."A BSF trooper was killed and three civilians injured in Pakistan army's unprovoked violation of bilateral ceasefire in Keran sector today (Saturday)."The army has retaliated effectively and intermittent firing exchanges were going on in the area when last reports came," police said here.The injured civilians have been shifted to hospital for treatment, they said, while identifying the killed BSF trooper as constable Nitin Subhash of Maharashtra. Though the LoC, which divides Jammu and Kashmir between India and Pakistan ss predominantly manned by the army, there are also some BSF posts on it.