Politically, the group’s long-term goal is ambitious in the extreme: It wants Hong Kong residents to be given a vote on the city’s future — including the option of independence — after 2047, when Beijing’s promise of civil liberties and a high degree of autonomy for the former British colony is set to expire. Analysts dismiss that as a fantasy.

More broadly, Hong Kong Indigenous, along with similar groups like Civic Passion, champions what has become known as “localism,” a reaction to mainland China’s growing influence here. Localists call for policies that favor Hong Kongers over mainland Chinese in areas like social benefits and school placement, and for defending Hong Kong traditions that they say are under threat. They have organized protests against shoppers from the mainland, and even against street performers who dance to songs in Mandarin Chinese, as opposed to Cantonese, the local dialect.

A Hong Kong tradition was a factor in the Mong Kok violence, which took place on the first night of the Lunar New Year holiday. In past years, the authorities had turned a blind eye to unlicensed street vendors who sold snacks like fish balls and stinky tofu to the holiday crowds. But this time, reports circulated that city inspectors were preventing Mong Kok vendors from selling their wares. (Officials later said that the inspectors had only been patrolling, and that no tickets had been issued.)

Using social media, Hong Kong Indigenous mobilized its followers to “protect” the vendors. Soon, some demonstrators were clashing with the police. At one point, an officer who was coming under attack fired live ammunition into the air — a shocking development in a city accustomed to peaceful protests. Before long, throngs of men in masks had set fires in the street and were hurling bricks at police officers, who struck back with batons and pepper spray and, in some cases, by throwing bricks themselves.