It was 81 days ago that Kamal Hussain Mondal, a 32-year-old brick factory worker from a remote village in West Bengal, took his own life. He had been a carefree man and attentive father to his two young sons, and was known throughout Soladana village for his devotion to his wife Khayrun Nahar Bibi. The pair had been married for 13 years but she spoke of their “puppy love”. He would feed her with his hands at mealtimes and on Sundays he would take her out on the back of his bicycle, telling others he loved simply riding through the fields together and chatting.

“He promised he would look after us for ever,” says Bibi. “But after he heard about NRC, everything changed and he fell into a deep despair. He told me: all Muslims are going to be driven from India now. They will lock us up or just kill us. Just wait and see.”

Facebook Twitter Pinterest Khayrun Nahar Bibi with her sons. Photograph: Shaikh Azizur Rahman

In mid-September, news that the government planned to carry out a National Register of Citizens (NRC) across India, to be implemented first in West Bengal, began to spread in this tiny village. The exercise will mean that every person in the country will have to prove they or their ancestors are citizens of India, rather than “infiltrators” from Bangladesh or Pakistan, and they will have to have the documentary evidence to back up their claim. According to the government, those who can not prove it will be sent to detention centres and face deportation.

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The BJP government insists that this vast bureaucratic endeavour is merely a long-overdue bid to count and identify citizens in India and to tackle illegal immigration. However the overwhelming fear among Muslims is that there is a far more sinister communal motive behind the exercise. The BJP openly subscribe to a Hindu nationalist agenda, aiming to establish the world’s largest democracy as a Hindu rather than secular state as enshrined in the constitution. The party’s past five years in power has seen the nation become divided down communal lines, with anti-Muslim hatred stirred up in the process. Since September, as several BJP politicians publicly vowed that “no Hindu will have to leave India because of NRC”, the Muslim community of West Bengal and beyond has grown increasingly worried that the NRC exercise seemed only to target them.

According to multiple accounts heard by the Guardian, over the past two months in villages across West Bengal, the RSS – the Hindu nationalist organisation that spawned the BJP – has also been conducting a covert campaign using its grassroots networks to reassure all Hindu households that they have nothing to worry about with the NRC, even if they have no supporting documents.

This week, the worst fears of the Muslim community were confirmed. A citizenship amendment bill (CAB), which was passed easily by parliament’s lower house on Monday and by the upper house at midnight on Wednesday, granted citizenship to migrants from Pakistan, Bangladesh and Afghanistan – but not if they are Muslim. It was signed into law early on Thursday morning.

The implications of this amendment are enormous. Should the NRC be carried out, it means that Muslims found without the correct documents will face the threat of being declared an illegal alien. Hindus, Sikhs and Jains are protected.

“This amendment undermines the entire secular foundations of India, it violates the constitution which states that no one can be discriminated against on the basis of identity and it threatens the very basis of Indian democracy,” says Kanhaiya Kumar, a student activist leading the charge against the NRC. “But most of all it sows communal poison and hatred by writing into law that Muslims are second-class citizens.”

The climate of fear that has seeped into Muslim communities across India since the nationwide NRC was proposed is increasingly palpable. In poorer communities in particular, it is common for people to have none of the necessary documents to prove their Indian citizenship, with the paperwork lost to flooding or fires or simply carelessness. Others have documents with incorrect information on them.

In Mondal’s case, it became too much to bear. While his family had only ever lived in India, he realised he was missing several key documents including his father’s birth certificate, while his own name was spelt differently across the paperwork he did have. “For almost a week he did not sleep or eat and he would stay up all night looking up NRC on his phone,” says Bibi. “He became very depressed, he would sit with his head against the wall or lie down on the floor in despair, telling me that we would certainly be driven out.”

Mondal had attempted to get his documents corrected online at the local cyber cafe, but struggled due to his illiteracy, and as the week went on, anxiety began to consume him. By that Saturday he had become quiet and withdrawn, only speaking to repeat his fears of being taken away, and when he slipped out of their bed at 4am on Sunday, Bibi presumed he was going to the market for an early cup of tea to ease his restlessness. But at 5.30am she was shaken awake by her sister-in-law. Mondal had killed himself.

Wiping away tears with her headscarf, Bibi said their youngest son, five-year-old Asadun, was still struggling to understand what had happened. “He keeps asking me if we get all the documents sorted, will my father come back?” she says. To date, at least 6 people have killed themselves in West Bengal over concerns related to the NRC.

The concerns are not unfounded. An NRC exercise was recently carried out in Assam, which resulted in 1.9 million people being left off the citizenship list for reasons as minor as spelling mistakes on their documents, and some for no definable reason at all. So-called “illegals” are due to be sent to detention centres at the end of December.

The Assam NRC was not initially designed to be rolled out nationwide; rather, it was originally based on decades-old legislation to help protect the indigenous Assamese people, both Muslim and Hindu. However, critics say it has been hijacked by the BJP as a way to sow religious discord and was reframed by the party as a means to weed out illegal Muslims. Observers note that it was only after discovering that 1.5 million Hindus in Assam had been left off the citizenship list that the BJP was prompted to introduce this week’s amendment, to ensure that if the NRC was rolled out nationwide, no more Hindus could be declared illegal.

Aparajita Bhuyan, BJP state spokesperson in Assam, was adamant that the measure was “not anti-Muslim” but added that all those Hindus in Assam found to be illegal would be given citizenship, while “after the Muslim illegal immigrants are identified in Assam, the government will decide what action would be taken against them.”

While 10 new detention centres are currently being built in Assam, and even more in West Bengal, questions remain over what the BJP government intends to do with the millions of detainees it will have on its hands after the NRC is rolled out. While it has publicly spoken of deportation, this will be impossible because neither Bangladesh, Pakistan nor Afghanistan has agreed to take them. It will similarly be too costly and impractical to keep everyone in prisons. One suggestion, already being proposed to companies in Assam, is that the detainees could be used as a huge cheap labour force in factories and industrial plants.

Days after the citizenship bill was first passed by parliament at the start of this week, its effect in stoking communal tensions was already evident. In the small West Bengal village of Ramnathpur, home to a predominately Muslim population, villagers spoke of “simmering tension’” that had arisen lately between Muslims and Hindus. “We are panicking because India is adopting the hate politics of Nazi Germany and we Muslims are the target,” said Maruf Hossain, 25.

Dilip Ghosh, president of the BJP in West Bengal, said the fear in the Muslim community was unfounded. “Muslims are perhaps scared because some groups or parties are misleading them on this issue,” said Ghosh. “Our prime minister and home minister have clearly said that Muslims should not have any reason to worry. All our [BJP] party leaders are also assuring them they should not be scared. This bill deals only with the non-Muslim minorities from the neighbouring countries. The bill has nothing to do with Indian Muslims. All Indian Muslims will remain citizens of this country.”

Yet it is not just those in rural communities that there is concern. One Muslim professor, who asked to remain unnamed out of fear of the authorities, said a “communal poison” had seeped into society in the past few months. “Muslims in India have a gun to their head now,” he said.

Shaikh Azizur Rahman contributed reporting

In the UK and Ireland, Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. Other international helplines can be found at www.befrienders.org. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14.