The Assam police has also filed an FIR under the anti-terror law UAPA against Imam for his speech.
The Delhi Police booked Sharjeel Imam, an activist who came in limelight during the ongoing protest in Shaheen Bagh, on Sunday for allegedly delivering inflammatory speeches against the amended Citizenship Act and the planned National Register of Citizens, officials said.
According to the police, Imam, a resident of Bihar and former Jawaharlal Nehru University student, delivered "very inflammatory and instigatory speeches in his opposition to CAA and NRC".
"He had previously delivered one such speech in Jamia Millia Islamia on December 13 last year and thereafter one even more inflammatory against the government which is being widely circulated on social media," they said.
These speeches have the "potential to harm the religious harmony" and the unity and integrity of India, for which the case was registered against him, police said.
Imam was heard saying in an audio clip that Assam should be cut off from the rest of India and taught a lesson, as Bengalis - both Hindus and Muslims - are being killed or put into detention centres.
He reportedly said that if he can organise five lakh people, it would become possible to "permanently cut off Assam with rest of India...if not permanently, then at least for a few months".
A case against Imam under IPC sections 124 A (an offence by words, either spoken or written causes disaffection against Government established by law), 153 A (promoting enmity between different religious groups with an intent to create disharmony) and 505 (statements conducing to public mischief) has been registered, the Delhi police said.
A case of sedition was lodged against Imam on Saturday for a speech he delivered on the Aligarh Muslim University (AMU) campus on January 16. The Assam police has also filed an FIR under the anti-terror law UAPA against Imam for his speech.