Hundreds of protesters took to the streets in India as Prime Minister Narendra Modi's government on Monday introduced a controversial bill in parliament that would give citizenship to non-Muslim minorities from three neighbouring countries: Bangladesh, Pakistan and Afghanistan.

Pakistan condemned the discriminatory legislation, saying it was "driven by a toxic mix of an extremist Hindutva ideology".

Prime Minister Imran Khan on Tuesday said the legislation "violates all norms of international human rights law and bilateral agreements with Pakistan".

Home Minister Amit Shah introduced the Citizenship Amendment Bill (CAB) in India's lower house amid raucous debate. Opposition parties stood against the proposed law that would, for the first time, create a legal pathway to grant Indian nationality on the basis of religion.

The bill was originally introduced in 2016 during the Modi government's first term but lapsed after protests and an alliance partner's withdrawal. It proposes to grant Indian citizenship to non-Muslims who came to India from Bangladesh, Pakistan and Afghanistan before 2015.

Oppositions politicians inside parliament, and protesters in several Indian cities, said the bill discriminated against Muslims and violated India's secular constitution. During a lengthy debate marked by angry exchanges, opposition Congress lawmaker Shashi Tharoor, according to AFP, said the bill "infringes upon the principle of equality before law" guaranteed to all persons, including non-citizens.

Shah and Modi's ruling Bharatiya Janata Party, which had included the CAB as part of its manifesto in the last general election, insist that it is necessary.

"In these three countries, Hindus, Buddhists, Sikhs, Jains, Parsis and Christians, followers of these six religions have been tormented," Shah alleged, before the bill was tabled after a vote.

Just after midnight, the bill comfortably passed the lower house with 311 votes in favour and 80 against, reported AFP. The bill has to be okayed by the upper house, where the ruling party does not have enough votes for passage. Any bill needs to be ratified by both houses of India's parliament to become law.

"This bill is in line with India's centuries old ethos of assimilation and belief in humanitarian values," Prime Minister Narendra Modi tweeted, adding that he was "delighted" about its passage.

But to Muslim organisations, rights groups and others, the bill is part of Modi's push to marginalise India's 200-million-strong Islamic minority.

Under Modi, several cities perceived to have Islamic-sounding names have been renamed, while some school textbooks have been altered to downplay Muslims' contributions to India.

In August, his administration rescinded the autonomy of Muslim-majority occupied Jammu and Kashmir — where a security and communication lockdown has been in place for over four months — and split it into two.

Pakistan slams controversial bill

In a statement issued by the Foreign Office, Pakistan condemned the move and said it was in "complete violation of the Universal Declaration of Human Rights and other international covenants on elimination of all forms of discrimination based on religion or belief".

"The Lok Sabha legislation is also in complete contravention of various bilateral agreements between Pakistan and India, particularly the one concerning security and rights of minorities in the respective countries.

"The latest legislation is another major step towards the realisation of the concept of ‘Hindu Rashtra’, idealised and relentlessly pursued by the right-wing Hindu leaders for several decades. It is driven by a toxic mix of an extremist ‘Hindutva’ ideology and hegemonic ambitions in the region.

"It is also a clear manifestation of interference in the internal matters of neighboring countries based on religion, which we reject completely," added the statement.

"Equally reprehensible are India’s pretensions of casting itself as a homeland for minorities allegedly persecuted in the neighboring countries. The massacre of thousands of Muslims in Gujarat, the Samjhauta Express carnage, innumerable lynchings by cow-vigilantes, repugnant schemes like Ghar wapsi and ‘Love Jihad’, and violence against Christians, Sikhs, Jains and even low-caste Dalits are the hallmarks of the new India ruled by the proponents of the extremist Hindu ideology.

"The continuing persecution of 8 million unarmed and innocent Kashmiris, collectively incarcerated and penalised by 900,000 Indian occupation forces, goes to further illustrate this blatantly extremist mindset. This Indian legislation has also, once again, exposed the hollowness of the claims to ‘secularism’ and ‘democracy’.

"We condemn the legislation as regressive and discriminatory, which is in violation of all relevant international conventions and norms, and a glaring attempt by India to interfere in the neighboring countries with malafide intent," said the statement.

'Last drop of blood'

Hundreds of demonstrators closed down streets in northeastern India on Tuesday as part of an 11-hour shutdown in protest of the legislation. The shutdown began at 5am (local time) and was organised by the North East Students Organization, an association of student groups from across India’s eight northeastern states.

They oppose the bill out of concern that more migrants will move to the border region and dilute the culture and political sway of indigenous tribal people.

Meanwhile, protesters on Monday returned to the streets in Assam — one of India's remote northeastern states that had previously opposed the bill — and blocked roads, burnt tyres and painted walls with slogans against the new proposal.

Student groups called for dawn-to-dusk shutdown in four districts of the state. Shops, businesses, educational and financial institutions remained shut and public transport stayed off the roads.

"We will fight and oppose the bill till the last drop of our blood," All Assam Students' Union adviser Samujjal Bhattacharya told Reuters, underlining the region's resistance against migrants amid fears that tens of thousands of settlers from neighbouring Bangladesh would gain citizenship.

In Modi's home state of Gujarat and the eastern city of Kolkata, hundreds of people staged protests and marched against the proposed law.

In a statement issued on Monday, a group of more than 1,000 Indian scientists and scholars also called for the immediate withdrawal of the bill.

"We fear, in particular, that the careful exclusion of Muslims from the ambit of the bill will greatly strain the pluralistic fabric of the country," the statement said.

"Please save this country from this law and save the home minister," Asaduddin Owaisi, an opposition MP from the All India Majlis-e-Ittehadul Muslimeen party, told parliament.