New Delhi, Jan 16 Anti-terror federal probe agency NIA has sent notices to over a dozen farm leaders, Sikh activists and journalists from Punjab, who are associated with the protest against Centre’s three farm laws, to appear before it as witnesses in a case pertaining to Sikhs for Justice (a banned outfit) legal adviser Gurpatwant Singh Pannun and his other associates. The move, among the protesting farmers, is seen as an attempt by the government to derail the agitation by intimidation. The farmer representatives, who held the ninth round of negotiations with the government on Friday, took strong exception and registered their objections to the notices being sent.