Police baton-charged people who gathered in Sardar Baug area of Ahmedabad on Thursday to protest against the Citizenship (Amendment) Act and the National Register of Citizens.
Nearly 200 people who had gathered in the area were dispersed to "maintain law and order" as they had not obtained permission to hold the protest, a police official said.
At least 20 protesters were also detained, he said.
"We had not given permission for this protest. We dispersed them to maintain law and order. We also detained some 20 people," inspector F M Nayab said.
The protest was organised by Left parties, including CPI and CPI(M), and organisations associated with them like the All India Democratic Students Organisations (DSO) and SUCI (Communist).
"Though we had officially taken permission for this agitation, it was cancelled at the last minute. However, we had announced yesterday that we will continue with our protest today. Around 200 to 300 people gathered at Sardar Baug today to protest against CAA and NRC," said Bhavik Raja, a member of the All India DSO.
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Demanding a rollback of CAA and NRC, some Muslim outfits also took out rallies in different parts of the state, including Morbi and Banaskantha districts.
The protesters held banners criticising the BJP-led central government for bringing the Citizenship (Amendment) Act and NRC.
Earlier, a call for Ahmedabad bandh was given by some groups here for Thursday.
In view of it, the city police on Wednesday said "no permission has been given for rally or protest on December 19".
In a tweet, they also urged people to adhere to law and call the police in case someone tries to "illegally take out a rally or tries to forcibly close shops".
The police said that the bandh called by a minority rights group in Ahmedabad evoked lukewarm response as routine life remained unaffected.