NEW DELHI — Wearing Muslim skullcaps, colorful turbans of Indian Sikhs or hip beanies of secular university students, thousands protested at the largest mosque in India’s capital on Friday, a turbulent scene that played out in multiple cities across the country. They defied government curfews, internet shutdowns and the divisive politics that have kept them apart for years.

The unrest, now in its second week and increasingly violent, started over a contentious citizenship law that favors every other South Asian faith over Islam. It has since evolved into a broader fight over what demonstrators say is an increasingly authoritarian government bent on dismantling India’s foundation: a secular nation that draws strength from its diversity.

“You just needed a trigger,” said Jasbir Singh, a Sikh information technology worker who joined the protests in Bangalore this past week. “In India, religion never decided your citizenship, and it should not in the future.”

More and more people are pouring into the streets, and many have clashed with police officers. On Friday, six protesters were killed in several towns in northern India, according to officials and the Indian news media, as officers used water cannons, tear gas, wooden sticks and — according to some reports — live ammunition against the demonstrators.