Swaraj Abhiyan President Yogendra Yadav was detained from the Red Fort, where prohibitory orders under Section 144 of the Criminal Procedure Code were imposed.
Appealing for peace, he asked people to continue the peaceful protest, but warned protesters not to commit any mistake that could dilute their rightful cause.
Left leaders including Communist Party of India-Marxist General Secretary Sitaram Yechury, Communist Party of India chief D. Raja and Brinda Karat of the CPI-M were also detained at the Mandi House area.
Former Congress MP Sandeep Dikshit was also detained at Mandi house as he reached to participate in the protest march from the Red Fort to the Shaheed Park.
"The police crackdown is uncalled for... police is working on the direction of the Union Government and is trying to suppress the dissenting voices but the government has failed on it as more people are coming out on streets to oppose the anti-people and divisive CAA," Dikshit said.
In view of the police crackdown at the Red Fort and Mandi House, the protestors were trying to assemble at the Jantar Mantar and despite the police barricading, protestors were assembling at different locations in central Delhi.
More than 16 metro stations were closed in view of the protests and internet services shut down in several areas of the capital.
( With inputs from IANS )