Guwahati, April 3 : After a threat was issued by a Khalistani outfit to Assam Chief Minister Himanta Biswa Sarma, the police on Monday reviewed the CM's security and also that of the airports and railway stations. A top police officer of the state told IANS that as of now, Chief Minister Sarma will continue to be a part of the existing security measures. He has Z+ security cover currently. However, police have stepped up the security vigilance at railway stations and airports across the state. Additional Director-General of Police (DGP) Hiren Nath has been looking after the security measures. An FIR was lodged on Sunday evening at the Special Task Force police station in Dispur. Earlier on Sunday evening, a section of journalists in Assam received calls from different mobile numbers. On receiving the calls, allegedly, a person claiming to be Gurpatwant Singh Pannu of 'Sikh for Justice' outfit issued 'threats' for Sarma. The voice said, "Pro-Khalistan supporters imprisoned in Assam have been tortured. Listen very carefully, CM Sarma, the fight is between pro-Khalistan Sikhs and the Indian regime. "We are seeking the liberation of Punjab from Indian occupation through the peaceful democratic process of Khalistan referendum. If your government is torturing and harassing the six, you will be held accountable," the voice added. G.P. Singh, Assam DGP, said, "Reference an audio clip threatening the Chief Minister of Assam by a person called Gurpatwant Singh Pannu, a designated individual terrorist under Indian law and heading an unlawful association called Sikhs for Justice (SFJ)." He added, "The security component of the Chief Minister has been adequately sensitised to the emerging threat. In view of global events, the threat is being taken very seriously by the Assam Police, and the central agencies have been kept in the loop on the issue." /IANS