NEW DELHI — As the temperature in India’s capital plunged on a recent evening, Rehana Khatun bundled her 29-day-old daughter in a fuzzy quilt and went out for her new nightly activity: participating in a sit-in against the government.

Khatun, 28, is a mother of three who rarely leaves her neighborhood in southeast Delhi. She is one of a few hundred Muslim women — including grandmothers and children — who have occupied a stretch of road for a month, undeterred by rain, cold or threats, as a sign of opposition to a new law that excludes Muslim migrants from a fast track to citizenship.

She sits cross-legged as she settles in for another night of speeches under bright blue and yellow tarps held up by narrow poles. “Our fight is for our constitution, our country, our survival,” she said.

The protest in the capital’s Shaheen Bagh neighborhood has become an enduring symbol of the demonstrations that have swept India over the new law, which was passed in December. Most of the women are homemakers, many in hijabs, and their long-running ­vigil has been featured on prime-time news shows, inspired similar sit-ins and attracted solidarity from across India. On Sunday, the protest attracted its largest crowd yet, according to locals, as thousands of supporters packed the narrow lanes surrounding the area.

Hundreds of thousands of people from around the country have taken to the streets in opposition to the law since its passage. Opponents say the measure is discriminatory and violates India’s secular ethos.

The protests mark the most significant challenge to the government of Prime Minister Narendra Modi since he took power in 2014. While India’s Muslim community is at the forefront of the opposition, Indians of all faiths have joined in the demonstrations, discontented with the government’s policies and its agenda of emphasizing Hindu primacy.

The government has shown no sign of backtracking from the citizenship law. On Monday, a member of Parliament from the ruling party said that any protester who damaged public property should be shot or jailed.

Several protests have devolved into showdowns with the police, who have responded with force. Since December, 24 people have died nationwide, nearly all of them in Uttar Pradesh, India’s largest state. People have registered their opposition in different ways, including candlelight vigils, readings of the Indian constitution’s preamble, and even a boat march by fishermen.

The peaceful sit-in at Shaheen Bagh began after police stormed a nearby university campus and assaulted unarmed student protesters. The first night, the demonstration consisted of four women and six men. In the following days, the men went to work, but the number of women coming out of their homes kept growing. Now the protest is led by women while the men watch from the sidelines.

Some women arrive in the morning, staying until the wee hours of the next day before going home for a few hours. When they leave, others take their place. The numbers change daily, ranging from several hundred to a few thousand. Children of all ages scamper around, waving national flags bigger than they are, while women cover their heads with the flag in a sign of reverence. They say they will not leave until the law is repealed.

“In all my 35 years of working with Muslim women, I had never witnessed a scene such as this,” activist Syeda Hameed, chair of the Muslim Women’s Forum, wrote after a visit. “What I was witnessing was the new generation of Muslim women who speak boldly without an iota of fear.”

Although there is no leader at Shaheen Bagh, some participants have already become icons. Bilkis, an 82-year-old grandmother who uses only one name, shot to fame after a viral television interview. Toothless and bent with age, Bilkis, now fondly called “Gangster Granny,” is protesting for the first time in her life.

“Our ancestors have also given their blood for this country,” she said, questioning why Muslims are being singled out by the government.

India’s powerful home minister, Amit Shah, has said the citizenship law will be followed by a nationwide push to verify all citizens, an exercise that many believe targets Muslims. Bilkis said that if the government goes ahead with the registry of citizens, she will refuse to participate. “They can beat us with sticks or shoot us with bullets,” she said. “We will die but won’t leave our land.”

From a small, rickety stage, participants make speeches about unity and the democratic traditions of the country and sing patriotic songs. Young and old recite poems: One favorite is a newly penned protest verse called “We won’t show our papers,” while others opt for a celebrated poem against dictatorship by a Pakistani poet.

On New Year’s Eve, the gathering swelled to several thousand. At midnight, the area reverberated with the national anthem and glowed with pinpoints of light from scores of phones held aloft.

Seema Saifi, 38, came out to protest on the first day and has since returned every day. She has barely slept in that time, traveling 40 miles round-trip each day to her job at a large company and joining the protest every evening until the early hours of the morning. She said the women have received messages of support from around the world.

“We have gotten strength from each other,” she said. “Now this seems like home.”

An army of nearly 200 volunteers, mostly locals or students living nearby, has split into teams to keep the sit-in running. Some look after meals while others coordinate with the media and guests. One day, a delivery truck rolled up with crates of milk and tea ordered by an anonymous well-wisher from Mumbai. A team of doctors started a medical tent that operates daily. A group of college students set up a booth where children can read and draw.

As the protest has endured, there have also been points of friction. There are arguments over who should be allowed on stage, whether to accept donations of supplies and how to keep away local politicians. Some chief volunteers recently tried to call off the protest to avoid its becoming a tool for political parties, but the women did not leave. Rumors about impending action by police to clear the road has not deterred them, either.

For Khatun, the past weeks of juggling household chores with ongoing protests have not been easy. Bringing out the newborn baby, whom locals call the youngest revolutionary, in the biting cold has its own risks. But she is unfazed.

“People take her in their lap when she cries. If she falls sick, there is a doctor here,” she said. When her daughter grows up and asks her what Khatun did at this moment, she said, “I will have an answer.”

Joanna Slater contributed to this report.