Sans any political affiliation or banner, the participants gathered well before noon at 15 sports in the city - which were designated as assembly points and held each other's hands to form the chain exactly as the clock struck 12 noon.
From top professionals like medicos, lawyers, teachers, professors, to those earning a living by cooking or washing utensils in others' homes - everybody joined in - some with the tri-colour in hand, while others had the national flag pinned to their chests.
The 15-minute chain stretched from the base of legendary revolutionary Netaji Subhas Chandra Bose's statue in north Kolkata's Shyambazar to Jadavpur University in the south.
The United Interfaith Foundation of India, a platform for people of all religious communities, organised the movement on behalf of the 'citizens of Kolkata' with the Roman Catholic Church playing a lead role.
"We are on the streets as we oppose CAA (Citizenship Amendment Act), NPR (National Population Register) and NRC (National Register of Citizens).
"We want rollback of this black Act," said Anubhav Sen, a middle aged man in south Kolkata's Golpark, likening the agitation to the one against the Rowlatt Act (that allowed certain political cases to be tried without juries and permitted internment of suspects without trial) in 1919 during the British rule.
"After huge protests erupted against the Rowlatt Act, the British government was forced to withdraw it. We will force the present central government to do the same," he said.
A woman - a teacher - standing beside him, alleged that CAA and NRC were causing schism in the country. "I don't want them. I want unity in our country."
Protesters also read the Preamble to the Indian Constitution at various areas of the city and the districts as the ongoing protests against the citizenship law merged with the observance of the monumental day in the history of independent India.
There was a virtual sea of people at South Kolkata's Park Circus - where the huge gathering of women since January 7 has given the place the appellation of Shaheen Bagh of the city of joy - as the tri-colour was hoisted and saluted and the Preamble read.
Hundreds of black balloons with the slogan "No CAA, No NRC, No NPR" were released, while at the centre of the park were garlanded pictures of national leaders - Mahatma Gandhi, Netaji and B.R. Ambedkar. "Fascibad ke chhati par, Gandhi, Subhas, Ambedkar' continues to be a popular slogan at the venue.
The massive show of strength saw the crowd spilling over to the nearby roads, stalling vehicular movement for some time.
"It is our pledge to protect the Constitution. People are so super excited, determined to carry on the protests," Uzma Alam, one of the organisers of the Park Circus protest, told .
Many of the participants also went to the near-by seven point crossing, and participated in the human chain.
"Today's programme was led by common people. Only the commoners participated. We didn't allow any political leaders," said Alam.
The protests also reverberated in the churches of the city and rest of the state during the Sunday morning prayers, as members of the Christian community read the Preamble together before joining the human chain.
Similar programmes were organised in the several other Shaheen Bagh like gatherings - varying in sizes - which have sprung up in Kolkata, neighbouring Howrah, and some even in remote districts.
( With inputs from IANS )