After a drive to root out illegal immigrants in the north-eastern Indian state of Assam put 1.9 million people at risk of being rendered stateless, the ruling Bharatiya Janata Party's (BJP's) promise of a similar nationwide drive to verify citizenship is causing unease and even panic.
Last month, Home Minister Amit Shah said the government is looking to expand the National Register of Citizens (NRC) from Assam to the rest of the country, in order to root out illegal immigrants.
While the government is unlikely to rush into nationwide implementation - a tough proposition in a country of 1.3 billion people - the mention of such a citizenship drive has led to much anxiety.
In West Bengal, a state bordering Assam, the media has reported cases of people lining up at government and municipal offices to amend mistakes in documents, and collect birth certificates and other documents.
The panic was triggered by BJP leaders saying Bengal will be next on the citizenship drive.
Dr Sujan Chakraborty, a Communist Party of India (Marxist) leader from West Bengal, said: "A climate is already created in Bengal following the publication of the NRC in Assam. Thousands of people are gathering at local offices, asking for corrections on their certificates, land mutations, other documents.
"It (NRC) is an attack against all, since the basis of citizenship is only a piece of paper. He or she who lacks that paper is suffering. Poor people who didn't have land records or other records are the ones who will suffer."
West Bengal Chief Minister Mamata Banerjee from the All India Trinamool Congress has said she will not let the register be implemented in the state. She claimed 11 people have committed suicide out of the fear that they would lose their citizenship.
"I will ask government officials and public representatives to visit every household in their respective areas and allay public fear," Indian media quoted her as saying.
The NRC was initiated in Assam, which shares a border with Bangladesh, to weed out Bangladeshi immigrants by creating a list of people who have the paperwork to prove they have lived in the state before March 24, 1971. Bangladesh declared independence from Pakistan on March 26.
Many people in Assam feel that the influx of immigrants from Bangladesh has been a threat to the local cultural identity.
Around 33 million residents were verified in the NRC process, while more than 1.9 million found themselves excluded. They have one more shot at appealing against their exclusion.
The implementation of the NRC has been widely acknowledged to be problematic.
BJP leaders in Assam like Mr Himanta Biswa Sarma, a powerful state minister, admitted the list was "faulty", and said the BJP would seek re-verification in some parts.
But the proposal to extend the NRC to other parts of the country has found support within the BJP in different areas, such as the states of Uttar Pradesh and Haryana.
The BJP has maintained that the NRC is necessary.
"For any nation, having complete details of its citizens and also non-citizens - both illegal and legal - is a basic requirement. India is primarily for Indians," said BJP spokesman Nalin Kohli, claiming that state after state has clamoured for the NRC.
Critics say the NRC could lead to social and religious unrest. Some BJP leaders have suggested Hindu immigrants fleeing neighbouring countries could be protected through new legislation.
Supreme Court lawyer Anas Tanwir, who runs the non-profit Indian Civil Liberties Union, has received dozens of calls from people worried about the NRC.
"I am getting calls, direct messages and text messages from people in West Bengal, Bihar and Uttar Pradesh because there is paranoia about the NRC. I tried to assuage concerns that it won't be the same as in Assam where you had to show documents from prior to 1951," said Mr Tanwir.
He added: "Rumours on WhatsApp groups are widespread."
Still, some political analysts remain doubtful whether the BJP will actually go ahead with a nationwide NRC, considering the problems in Assam.
"I think they will use it as rhetoric," said Dr Sandeep Shastri, pro-vice-chancellor of Jain University. "Policy implementation will be difficult. It's complicated, it's sensitive and it is likely to have a backlash."
