Authorities deployed thousands of paramilitaries and blocked mobile internet in northeast India yesterday, while police fired blank rounds at protesters who defied a curfew to demonstrate against contentious new citizenship legislation. A railway station in Dibrugarh's Chabua of Assam state was set on fire by protestors late in the night after the upper house passed the contentious Citizenship Amendment Bill (CAB) allowing the fast-tracking of citizenship applications from religious minorities from three neighbouring countries, but not Muslims. For Islamic groups, the opposition, rights groups and others in India, the new law is part of Prime Minister Narendra Modi's Hindu-nationalist agenda to marginalise India's 200 million Muslims, something he denies.

But many in India's far-flung northeast object because they fear the legislation, which prompted angry exchanges in parliament this week, will give citizenship to Hindu immigrants from Bangladesh.

Five thousand paramilitary forces were deployed in the city of Guwahati in Assam state, while many roads and highways were blocked to prevent the spread of protests.

Officials said 20-30 people have been hurt in the demonstrations in recent days, with vehicles torched and police firing tear gas and charging the crowds with heavy wooden sticks.

Guwahati's top police officer Deepak Kumar was removed from his post and replaced over the outbreak of violence, authorities said.

All train services to Tripura and Assam were suspended and some flights were

cancelled. Several cricket and football matches scheduled to take place in Assam were called off amid the curfew.

Modi sought to calm the situation in a series of tweets that many in the region could not read because mobile internet was blocked in some areas.

"I appeal to the northeast, to Assam and every other state -- every community there -- to assure that their culture, traditions and language will keep getting the respect and support," he added at a rally at eastern Jharkhand state.

"Assam is not a dustbin so that central government will keep on dumping whoever they want in Assam," Assamese film actress Barsha Rani Bishaya said in Guwahati at a meeting of film and student bodies.

"People of Assam have woke up against the CAB this time and they will not accept the CAB."

Several leaders from Modi's ruling Bharatiya Janata Party (BJP) in Assam have also resigned in opposition to the legislation.

Meanwhile, Bangladesh Foreign Minister A.K. Abdul Momen cancelled a trip to New Delhi hours before he was due to arrive Thursday, citing domestic engagements.

He had on Wednesday pushed back against the Indian government's claims the legislation was meant to help those persecuted in Bangladesh, Pakistan and Afghanistan, telling local media his country did not oppress minorities.

It is not yet clear if the legislation, after being signed off by the president, would survive a constitutional challenge in the Supreme Court.

The Indian Union Muslim League filed a petition in the top court, with the political party's leader saying it was against the basic principles of the country's constitution.

"The constitution says there will be no differentiation based on caste, religion or anything. Here, the citizenship is being given on the basis of religion," P.K. Kunhalikutty told AFP.

"The CAB... won't stand in front of the law."

The petition states that they "do not have any grievances in granting citizenship to migrants but the petitioners grievances is directed against discrimination and unreasonable classification based on religion."

Amnesty International said the law was "bigoted" and called for it to be immediately repealed.

"In a secular country like India, slamming the door on persecuted Muslims and other communities merely for their faith reeks of fear mongering and bigotry," the global rights groups said in a statement Wednesday.

"They also run absolutely foul of India's international obligations."

PTI adds: A railway station in Dibrugarh's Chabua, the hometown of the chief minister, was set on fire by protestors late in the night. The Panitola railway station in Tinsukia district was also torched, a Northeast Frontier Railway spokesperson said.

Some student leaders, who went live on national TV, claimed many agitators were injured in police action in front of the secretariat.

According to unofficial accounts, hundreds of protesters have been detained in Guwahati and other places like Dibrugarh and Jorhat.

Similar incidents were reported from Tripura capital Agartala.

Police opened fire in Assam capital Dispur to quell a protest by the agitators after water cannons, baton-charge and tear gas failed to rein them in. Police also fired at Ulubari, which is barely 500 m from the state police headquarters.

A large number of agitated students blocked the road near the secretariat complex and pulled down the barricade erected on the arterial G S Road, provoking police action.

Police burst teargas shells and baton-charged the protesters, who were seen lobbing back the shells at men in uniform.