Earlier, Assam Police Director General Bhaskar Jyoti Mahanta said the curfew will be in place till 7 am on Thursday.
In Dibrugarh, curfew was imposed on Wednesday night and will be in force till further orders, Deputy Commissioner Pallav Gopal Jha said.
The Army was deployed in four districts to quell the protests.
Army PRO Lt Col P Khongsai said two Army columns have been deployed in Guwahati city and are carrying out flag marches.
The Army has also been deployed in Tinsukia and Dibrugarh districts, officials sad.
Late night Army was called in at Jorhat and its personnel were staging flag march, Deputy Commissioner Roshni Korati told PTI.
Tens of thousands of protesters against the CAB descended on the streets of Assam, clashing with police and plunging the state into chaos of a magnitude unseen since the violent six-year movement by students that ended with the signing of the Assam accord.
Though no party or student body has called a shutdown, protesters, a majority of them students, fought pitched battles with security forces in the restive state, including in front of the secretariat, the seat of the BJP government.
Police fired tear gas shells and baton-charged protesters, who fought back.
The Citizenship (Amendment) Bill, 2019, which has already been approved by Lok Sabha and Rajya Sabha, proposes to give citizenship to Hindus, Christians, Parsis, Jains, Budhists and Sikhs facing religion persecution in Pakistan, Bangladesh and Afghanistan.