The death toll from violent protests against a new citizenship law in  India has risen to six, including four shot by police, with authorities maintaining internet bans and curfews in some northeastern regions.

Tension remained high for a fifth straight day in Assam state’s biggest city, Guwahati, as 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, the AFP news agency quoted the local officials as saying.

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 buy 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.

Old wounds re-opened in Assam

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 or who flowed in around Bangladesh’s 1971 war of independence.

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.”

On Sunday, Home Minister Amit Shah called 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.

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.