Radical preacher and pro-Khalistan separatist Amritpal Singh has been flown to Dibrugarh in Assam where eight of his associates, including main aide Papalpreet Singh, are already being held under the National Security Act, which allows detention up to a year without any charge. He was arrested this morning after he surrendered before the police after addressing a gathering in a gurdwara in Punjab's Moga, sources told NDTV.