Assam police on Sunday “appropriately tightened” the security of Himanta Biswa Sarma following the emergence of a pre-recorded audio clip purportedly circulated by a pro-Khalistan leader, Gurpatwant Singh Pannun, “threatening” the chief minister.

Assam director general of police G.P. Singh said on Sunday evening they received information in the afternoon from “some” media friends about the receipt of a pre-recorded audio clip of a person called Gurpatwant Singh Pannun “threatening” the chief minister “on various counts relating to the Sikh community in Assam”.

Singh said a case had been registered with the special task force police station here under “appropriate” sections of the IPC and the UAPA and they would be launching an investigation.

Assam has been in the news following the crackdown on suspected aides of Khalistan sympathiser and radical preacher Amritpal Singh in Punjab last month. As many as eight people linked to Waris Punjab De, the outfit helmed by Singh, were shifted to Dibrugarh central jail in upper Assam after their arrest last month.

Amritpal Singh is still absconding.

Sources said the US-based Pannun is a “designated” terrorist under the UAPA and heads the Sikhs for Justice (SFJ), an association banned by the Centre in 2019 for “indulging” in secessionist activities in Punjab. The SFJ was formed in the US in 2007.

A journalist familiar with the content of the audio clip told The Telegraph that Pannun had alleged pro-Khalistan supporters lodged in Assam jail were being tortured and that Sarma would be held accountable if those imprisoned were tortured and harassed by the government.