New Delhi, India - Thousands of protesters have gathered in a predominantly-Muslim neighbourhood in India's capital as the country celebrated Republic Day to commemorate the day its constitution came into effect.

Sarwari, 75, who goes by her first name, was among a group of women invited on Sunday to unfurl the tricolour - India's national flag - amid loud chants of the national anthem at Shaheen Bagh, the main site of protest in New Delhi.

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About 15 kilometres (nine miles) away in the heart of the capital, Indian President Ram Nath Kovind hosted his Brazilian counterpart Jair Bolsonaro, the Republic Day chief guest this year, as they watched the annual parade aimed at showcasing India's military might and cultural diversity.

Indian Prime Minister Narendra Modi, who the protesters accuse of pursuing a Hindu supremacist agenda, also attended the government event.

For 42 days, mainly Muslim women protesters have blocked a highway in New Delhi to protest against the CAA [Nasir Kachroo/Al Jazeera]

Epicentre of the protests

For 42 days now, demonstrators, mainly Muslim women, have blocked a highway in the southeastern part of the Indian capital to protest against the Citizenship Amendment Act (CAA), passed by Parliament last month.

The CAA fast-tracks the naturalisation of non-Muslim immigrants from Pakistan, Bangladesh and Afghanistan, who came to India before 2015.

What's Hindu nationalism and what does Indian Prime Minister Narendra Modi have to do with it? pic.twitter.com/lNuumLm1oX — AJ+ (@ajplus) January 26, 2020

Critics say the law violates India's secular constitution and is a step towards marginalising the country's 200 million Muslims, who form nearly 15 percent of India's 1.3 billion people.

Coupled with a proposed National Register of Citizens (NRC) and a continuing National Population Register (NPR) exercise, Muslims fear the move will force them to show documentation to prove their nationality.

India's governing Hindu nationalist Bharatiya Janata Party (BJP) dismisses those fears and calls the protests "misguided".

But daily protests across India have been demanding a rollback of the CAA and an assurance from the government that no Indian citizen will be forced to prove their nationality.

'Fight for the soul of India'

On Sunday, as the clock struck midnight, protesters at Shaheen Bagh read out the preamble to the Indian constitution, which on this day in 1950, came into effect.

Sarwari, 75, was one of the women who unfurled the Indian flag at Shaheen Bagh [Nasir Kachroo/Al Jazeera]

"It was an honour for me," Sarwari told Al Jazeera. "I had never taken part in any flag hoisting event before."

Around her were thousands of people, carrying the national flag and raising slogans. Many had painted their faces with the tricolour, while hundreds of women, wearing burqas - black full-body veils that cover the face as well - were seen with tricoloured-fabric and ribbons wrapped around them. Children ran around, waving little flags.

"This is a historic day for all of us," Abid Ahmed, a resident of Shaheen Bagh, told Al Jazeera.

"We impress upon the government to understand the preamble of our constitution and in light of that announce a rollback of the controversial law. The law is in contravention of the constitution."

Insha Hussain, a 16-year-old student who had been participating in the Shaheen Bagh protest since the middle of December, told Al Jazeera their "fight is for the soul of India".

"Our constitution which was adopted on this day 70 years ago is the soul of our nation and we are out to protect that soul," she said.

"It's shameful that after 73 years of independence, our focus should be on providing jobs to people, not to prove our citizenship."

Indian protesters are demanding a withdrawal of the controversial citizenship law [Nasir Kachroo/Al Jazeera]

Massive human chains

Similar "Save the constitution" events were held at other sites in New Delhi and in Kolkata, Bengaluru, Hyderabad, Mumbai, Lucknow and other cities.

In the southern state of Kerala, hundreds of thousands of people formed a 620km (385-mile) human chain from Kasaragod in the north to Kaliyakkavilai in the south, demanding the CAA's withdrawal.

The massive protest was organised by the governing Left Democratic Front party, with Chief Minister Pinarayi Vijayan himself joining in the state capital, Thiruvananthapuram.

"The movement in Kerala is to resist attempts to undermine India's secular fabric, its plural ethos, federal structure and democratic values," politician S Ramachandran Pillai, who flagged off the protest at Kasargod, told Al Jazeera.

Pillai said the human chain was one of the largest mass mobilisations ever in Kerala. "The central government will be forced to withdraw [the citizenship law]," he said.

Protesters in Kolkata city organised an 11km human chain [Ronny Sen/Al Jazeera]

In the eastern state of West Bengal, thousands in the capital Kolkata also formed an 11km (seven-mile) human chain.

The protest in Kolkata was organised by the United Interfaith Foundation India, a group comprising leaders of different religious communities in the state.

"Almost two million people have been left out in the final NRC list in Assam and many are already in detention camps," Priyankar Dey, who was part of the human chain in Kolkata, told Al Jazeera, referring to the northeastern state where the NRC exercise was first carried out.

"CAA, NRC and NPR are inherently discriminatory. The human chain today is a message to everyone in power that we Indians are all together in this fight," he said.

Additional reporting by Leena Reghunath from Kerala and Ronny Sen in Kolkata