KARAIBIL, INDIA (AFP) - Indian farmer Nur Mohammed can barely sleep for worrying that his wife might soon be made stateless, put in a detention camp and deported.
She is one of four million people left off a draft National Register of Citizens published in July in the north-eastern state of Assam - provoking accusations of discrimination against Muslim residents and of stoking ethnic tensions.
Those not on the list, who could now face being effectively stripped of their Indian citizenship and rights, can challenge their omission by providing certain documents to prove they are legal residents - but many lack the necessary paperwork, and the Dec 31 deadline is looming.
"We are genuine Indian citizens," said Mr Mohammed, 66, his voice low and quivering.
"While my name, the names of my two sons and daughter appeared in the list, the name of my wife is not there," he told AFP.
The draft list excludes all those unable to prove they were in the state before 1971, when millions fled Bangladesh's war of independence and sought refuge in Assam and elsewhere.
Those born in Assam after 1971 have to prove that their parents or grandparents entered India before that. But getting hold of documents in a state where many are illiterate and lack even basic papers is a challenge.
Less than two weeks before the deadline, only around 1.5 million people left off the draft list have submitted claims to be included, the Assam government says.
"There is large-scale illiteracy in our area, people don't have access even to basic education," said Mr Akram Hussain, an activist helping people file claims.
"They have been living like this for ages but now all of a sudden they are being asked to bring documents to prove their identity."
Mr Mohammed's wife Yarjan Nesa submitted a certificate issued by the head of her village in the rural district of Kamrup to establish her link with her mother, but it was rejected.
"I do not have any other document as I have never been to school or never had a bank account anywhere," she said.
Assam has seen many major influxes in India's turbulent history, beginning when the British colonial rulers brought in Bengalis to work on tea plantations.
Immigration continued after independence in 1947, and today, Bengali speakers make up around 30 per cent of Assam's 31 million people.
Tensions in the ethnic and religious melting pot have at times boiled over into violence - 2,000 Bengalis were butchered in one day in 1983 - and have increased pressure for a lasting political solution.
The first, failed, attempt at screening in Assam was made in 1951.
In 2008, a prominent Assamese campaigner lobbied India's Supreme Court - six years later, the court ordered the federal government to update its citizens register.
Critics say the process is being used by Prime Minister Narendra Modi's Hindu nationalist BJP party - which runs Assam - to stoke anti-Muslim feelings ahead of elections in 2019.
Some two-thirds of the Bengalis are Muslim, the rest Hindu. Assamese speakers, the largest community, are mostly Hindu.
United Nations special rapporteurs expressed "serious concerns" in a recent letter to the Indian government about the process "stoking ethnic tensions".
Mr Abdul Kalam Azad, a local researcher and activist, says he has recorded at least 26 related suicides since the National Register of Citizens process began in 2015. The impact on mental health is set to be a "huge problem", he told AFP.
Prime Minister Modi's government has said no genuine Indian would be left off the register but Mr Amit Shah, Mr Modi's right-hand man, has said India must act against "infiltrators who were eating the country like termites".
Activists say claims get rejected due to minor errors and that even some officials are confused.
Bengali-speaker Baharjan Nesa, 88, said she was left off with her son and daughter-in-law even though she has a copy of a 1954 Indian electoral roll featuring her father's name.
Others omitted include Hajong people who arrived in the 1960s from what is now Bangladesh and were given refugee status.
Once the Dec 31 deadline has passed, a verification process begins in February.
What will happen to those who still do not make the cut remains to be seen - with some hardliners calling for mass deportations.
Ominously, 1,037 people including 31 minors have already been put in six cramped detention camps. Reports say a seventh camp with capacity for 3,000 people is being built.
Bangladesh has stated that it will not accept any deportees and Mr Modi has reportedly told Dhaka that this is not on the cards.
But even if people are not moved en masse to camps or ejected, becoming effectively stateless could make normal life - accessing healthcare or education - much tougher.