NEW DELHI - Six people have died, including four who were shot dead by police, following violent protests in northeast India over the contentious citizenship law, with authorities maintaining internet bans and curfews in some regions.

Tension remained high at the epicentre of the unrest in Assam state’s biggest city, Guwahati, over the legislation amid curfew.

In Assam, four people died in hospital after being shot, while another died when a shop he was sleeping in was set on fire and a sixth after he was beaten up during a protest, officials said.

Train services were also suspended in some parts of the east on Sunday after violence in eastern West Bengal state, with demonstrators torching trains and buses.

Indian Home Minister Amit Shah has called again for calm, saying local cultures in northeastern states were not under threat, amid fears the new law will grant citizenship to large numbers of immigrants from neighbouring Bangladesh.

“Culture, language, social identity and political rights of our brothers and sisters from northeast will remain intact,” Shah told a rally in eastern Jharkhand state, News18 television network reported him as saying.

Tension remained high for a fifth straight day in Assam state’s biggest city, Guwahati. Some 5,000 people took part in a fresh demonstration in Guwahati on Sunday, with hundreds of police watching on as they sang, chanted and carried banners with the words: “Long live Assam”.

Officials said oil and gas production in the state was hit by the curfew, although the restrictions were eased during the day on Sunday with some shops opening.

Violent protests have raged in Assam since India’s parliament passed the new law on Wednesday, which allows New Delhi to grant citizenship to undocumented immigrants who entered India from three neighbouring countries on or before December 31, 2014 - but not if they are Muslim. Critics say the law, pushed by Prime Minister Narendra Modi’s Hindu nationalist government, violates the secular principles of India’s constitution by discriminating against a community.

But the new law has also reopened old wounds in Assam state, a region sandwiched between Bangladesh, China and Myanmar which has long seethed with interethnic tensions and where armed tribal groups are still resisting being a part of India.

Assam has long seen hostility between locals and Bengali-speaking immigrants brought by the British to toil on tea plantations.

Years of agitation driven by student organisations that included the 1983 Nellie massacre - when at least 2,000 people were butchered in six hours - only ended in 1985 with the Assam Accord.

Journalist Sangeeta Barooah Pisharoty, who works for The Wire website, told Al Jazeera that Assamese people see the new law as a “direct violation” of the 1985 accord. “The accord was to allow all who had come to Assam until 1971 to be citizens, not December 2014 as this new law says,” she said. “When you try to tinker with that, you’re actually setting off a fire.”

Meanwhile, in the neighbouring state of West Bengal, demonstrators on Sunday set fire to tyres, staged sit-ins on highways and railway tracks, and torched trains and buses to protest the citizenship law.

Riot police was brought in to disperse protesters and train services suspended in some parts of eastern India.

West Bengal Chief Minister Mamata Banerjee - who has spoken out against the national government’s push for the law - suspended internet services in several districts of the state.

In capital New Delhi, the police once again baton-charged and used tear gas shells to disperse thousands of protesters at the Jamia Millia Islamia University. “Police entered inside the campus and chased the students who were protesting peacefully, creating panic,” Amit, a student of law, told Al Jazeera.

Another student, requesting anonymity over fears of reprisal, said: “I have never witnessed this before in my life. This is a university, not a battlefield.”

Indian media reports said the protesters set fire to two city buses and roads in the area were blocked.

In a statement released to the media, the students and teachers of Jamia Millia Islamia University condemned the violence and said “many locals” had joined the protest. “We have time and again maintained that our protests are peaceful and non-violent. We stand by this approach and condemn any party involved in the violence,” said the statement.

“Violence by certain elements is an attempt to vilify and discredit genuine protests,” it said.

India’s opposition parties, rights activists and others see the new law as part of Modi’s agenda to marginalise India’s 200 million Muslims.

The main opposition Congress party held a rally in the capital, New Delhi, on Saturday, where its interim president Sonia Gandhi called the citizenship bill “dangerous”.

“Modi and Shah [PM Modi and Home Minister Shah] don’t care. This citizenship amendment bill they brought in recently will shatter the soul of India, like what is happening in Assam and the northeastern states of the country.”

Speaking to Al Jazeera, Swaraj India party’s founder Yogendra Yadav used a Nazi analogy to explain the implications of the new law. “It is the beginning of something very pernicious. You first put a star, then you put people in a ghetto and then you finally take them to the end-point,” he said.

“This, unfortunately, could be the beginning of what could result in disenfranchisement of a very significant population in India.”