"We will investigate the matter as per the law," senior police official said.
A case was registered against powerful Assam minister Himanta Biswa Sarma for allegedly promoting enmity between different groups by making "false statements", days after he claimed on social media that AIUDF supporters raised "Pakistan Zindabad" slogans at the Silchar airport, police said on Tuesday.
The case was lodged on the basis of a complaint filed by the Congress on Monday at the Bhangagarh police station in Guwahati, they said.
Mr Sarma and a brigade of BJP leaders on November 5 slammed the supporters of AIUDF president Badruddin Ajmal, alleging that they had raised "Pakistan Zindabad" slogans at the Silchar airport, but the opposition party refuted it and said the BJP twisted the "Aziz Khan Zindabad" slogan.
"A case was registered under relevant sections. We will investigate the matter as per the law," a senior police official told PTI.
Another official said that the case has been registered under IPC Sections of promoting enmity between different groups and attempting to commit offences punishable with imprisonment for life or other imprisonment.
"These sections will be read with Section 67 (publishing or transmitting obscene material in electronic form) of the IT Act," he added.
The slogans were raised as Aziz Ahmed Khan, the AIUDF MLA from Karimganj South constituency, was accompanying Ajmal, a Lok Sabha MP, at the airport in Silchar in the linguistically and religiously sensitive Barak Valley.
"Look at the brazenness of these fundamentalists anti-national people who are shouting PAKISTAN ZINDABAD while they welcome MP Badruddin Ajmal. This thoroughly exposes Indian National Congress which is encouraging such forces by forging an alliance. We shall fight them tooth and nail. Jai Hind," Mr Sarma had said on Facebook.
Mr Sarma, the convenor of the BJP-led North East Democratic Alliance NEDA), is a powerful politician of the region and holds most of the key portfolios in the Assam government, including Finance, Health and Education.
In the complaint filed by state Congress general secretary Ranjan Bora, it was alleged that Sarma has the "habit" of making "communally sensitive" remarks, and such a statement was made about the slogans raised at the Silchar airport to create "disharmony between different groups".
"It will be pertinent to mention herein that the said accused person had a habit of making loose and communally sensitive statements and at a time when assembly elections are around the corner, such statement can create communal tension," it added.
The complaint also pointed out that Facebook had flagged the post by Mr Sarma as "false and fake" after getting it verified by third-party fact-checkers.
A day after the video was uploaded by Mr Sarma, Facebook said, "Independent fact-checkers say that this information has no basis in fact."
Facebook had also blocked the video from auto-play. However, Facebook has now withdrawn its note of caution on the video without any explanation.
Silchar's BJP MP Rajdeep Roy said he had filed a complaint with the police against Ajmal and AIUDF supporters over the slogans.
The AIUDF is part of the "Grand Alliance" being forged by the Congress against the ruling BJP and its allies for the state assembly elections, likely to be held next year.