The demonstrations were triggered by a controversial bill which would have allowed extraditions to mainland China, but have evolved into a call for wider democratic reforms and a halt to sliding freedoms.
Saturday’s violence compounds the political crisis with the city’s leadership seemingly unable, or unwilling, to end the chaos.
Yuen Long is in Hong Kong’s New Territories, a rural area where many of the surrounding villages are known for triad connections and their staunch support for the pro-Beijing establishment.
Police say they have arrested 12 people so far in connection with Sunday’s violence, nine of whom have known triad links.
The white shirt mob ran into two villages near Yuen Long station after their attack and later left without police making any arrests despite a large presence of officers.
These two villages became the focus of protester anger on Saturday.
The rally began peacefully. But small groups of more hardcore protesters, many in helmets and carrying shields, confronted police outside the villages and accused them of protecting triads.