Authorities have banned gatherings including all of Uttar Pradesh and Bangalore, areas of the northeast and parts of Bihar, New Delhi, Hyderabad and Chennai.
Police opened fire on hundreds of protesters in southern India on Thursday, killing two, an official said, as fresh violence erupted around the country over a contentious citizenship law critics say is anti-Muslim.
The fatalities brought to eight the death toll from more than a week of unrest and came as authorities shut down internet and text messaging for tens of millions in India's most-populous state.
In the southern city of Mangalore, two men identified as Abdul Jalil, 49, and Samshir Kudroli, 23, "died in police firing during the protests", Qadir Shah, a spokesman for the deputy commissioner, told AFP.
He said a curfew had been imposed in the city with schools, restaurants and bars shut.
A third fatality was also reportedly linked to protests in the northern state of Uttar Pradesh, where a man was hospitalised in Lucknow with a gunshot injury and died soon after, a hospital source told AFP.
Police did not confirm the death, but his father told the Times of India his son was shot after getting caught in a crowd of protesters while out to buy groceries.
Four others were being treated at a hospital in Mangalore "with bullet injuries following the clashes", a district medical officer told AFP.
In this video, why is the cop firing bullets at people in Mangalore, Karnataka?— Srivatsa (@srivatsayb) December 19, 2019
Was there any shoot at sight orders by the DM!?
CM Yediyurappa and Home Minister must answer as to what's happening.pic.twitter.com/xHzOkq2cey
Ban on protests
Historian Ramchandra Guha, a biographer of independence leader Mohandas Gandhi, was among those detained in Bangalore, the capital of southern Karnataka state.
The state government issued a ban on groups of more than four people gathering.
Reached by phone, Guha said he was in a bus with other detainees and did not know where the police were taking them.
In New Delhi, Yogendra Yadav, the chief of the Swaraj India party, was among those detained as protesters demonstrated at New Delhi's iconic Red Fort and the surrounding historic district.
Officials said more than 100 people were detained at the fort.
The protesters were loaded into buses and other vehicles. The main roads leading to the fort were blocked off and police did not let pedestrians go to nearby temples or shopping areas.
One of India’s leading public intellectuals! SHAMEFUL!!!! 😡😡😡😡 https://t.co/EndCKTCDZm— Swara Bhasker (@ReallySwara) December 19, 2019
Communications blackout in Delhi, India's capital, to thwart protests against Modi govt's bigoted, unconstitutional and dangerous #CitizenshipAmendmentAct #IndiaRejectsCAA— Shehla Rashid (@Shehla_Rashid) December 19, 2019
Mobile internet around Lajpat Nagar and Jangpura seems to be affected. Internet at Jantar Mantar v. slow pic.twitter.com/Jao90oVN08
Mobile services partially suspended
Two major Indian telecom firms also said on Thursday that they have cut mobile services in parts of New Delhi on government orders.
Mobile carrier Vodafone Idea said the company had suspended internet services in some parts of the capital Delhi to comply.
SMS services have also been suspended at a few locations, the company's customer care separately told another Twitter user.
Rival Bharti Airtel's customer care also told customers on Twitter it had suspended voice calls, SMS and internet services in parts of the Indian capital following days of protests across the city against a new citizenship law.
Indian Prime Minister Narendra Modi's move to drive the law through parliament last week has ignited nationwide protests that have often turned violent, with six people killed.
The law gives migrants fleeing persecution from neighbouring Afghanistan, Pakistan and Bangladesh an easier path to citizenship, except that Muslims are excluded.
Critics say it is further proof that Modi, emboldened by a resounding election victory this year, is moving quickly to reshape India as a Hindu nation and weaken its secular foundations.
During the past week of unrest, hundreds of people have been arrested, authorities have cut the internet in some flashpoint areas and banned large gatherings in others.
Police have fired tear gas into crowds and been accused of beating protesters, including women and students, fuelling the anger.
India getting a glimpse of everyday life in Kashmir— Rana Ayyub (@RanaAyyub) December 19, 2019
Centrestage - New Delhi
Protest organisers flagged plans for major rallies on Thursday in major cities across India, including the capital of New Delhi.
Police refused a march permit for one of two major demonstrations planned in New Delhi, officials said. Organisers said they planned to march anyway.
Authorities on Wednesday also imposed a ban on gatherings of more than four people in some of the city's Muslim-dominated districts.
A crowd of mostly young people rallied outside Delhi's Jamia Millia Islamia, a public university, on Wednesday to protest, defying the ban on large gatherings.
"We are really very angry with the BJP government... they have taken racism to the extreme point," Taiba Hadis, 18, said at the rally.
"They are questioning our existence, and it is high time for us to speak up."
In the financial capital of Mumbai, hundreds of people rallied on Wednesday carrying placards with the words: "India is Ours" and chanting "We Are All One".
"We just cannot go along with this bill. I can't believe we now have to prove our citizenship after living in India for so many years," Tabeer Rizvi told AFP as the Mumbai crowd burst into a Hindi version of the US civil rights movement anthem: "We shall overcome".
"I am not surprised to see people of all religions come out to protest this bill."
Rallies were also held in other states including West Bengal, Tamil Nadu and Telangana on Wednesday.
UN secretary general's spokesman Stephane Dujarric said Tuesday the global body was "concerned about the violence and alleged use of excessive force by security forces that we've seen that have been taking place".
The US State Department this week urged New Delhi to "protect the rights of its religious minorities in keeping with India's constitution and democratic values".
US-India agree to cooperate amid domestic chaos
The US and India agreed on Wednesday to expand defence, science and technology cooperation as Secretary of State Mike Pompeo said impeachment would not distract the Trump administration on national security matters
Pompeo and Defense Secretary Mark Esper met their Indian counterparts for security talks at the State Department as the House debated charges against President Donald Trump. Trump was later impeached by the House, Senate trial pending.
Pompeo said “the noise and silliness” in Washington would not affect the administration's focus on US national security.
The US and India are each dealing with domestic political crises: the US with impeachment, India with widespread protests and violent clashes in India over a new citizenship law.
“The world should know that despite all the noise, the chaos, the media asking questions that are completely unrelated to the reason we are here today, that the leaders of our two nations are working diligently to protect the American people, to develop a relationship that’s important strategically for the coming decades between the United States and India,” Pompeo said.
"We won’t let the noise and the silliness in Washington, DC, distract us from that,” he a news conference with Esper, Indian Foreign Minister Subrahmanyam Jaishankar and Indian Defense Minister Rajnath Singh.
Asked whether he would participate as a witness in a Senate trial if the House impeached Trump, Pompeo said he would produce State Department documents and testify if the requests were “appropriate and required by law."