Hong Kong police have fired tear gas at an unauthorised protest involving thousands of demonstrators.
Protesters had been marching through the northern district of Yuen Long, condemning an assault on pro-democracy protesters by armed masked men that took place there last week.
Protesters had accused the police of turning a blind eye and colluding with the attackers – claims the police deny.
Hong Kong has seen seven weeks of anti-government and pro-democracy protests.
The protests were sparked by a controversial bill that would have enabled extraditions to mainland China.
The government has since halted the legislation – but protesters are now also demanding an inquiry into police violence, democratic reform, and that the territory’s leader Carrie Lam resign.
Saturday’s march had been banned by the police – a highly unusual move in the territory – as they said they feared there would be violence.
Despite this, several thousand protesters still converged in Yuen Long, chanting anti-police slogans.
The rally was planned as a response to last Sunday’s attack, where about 100 men in white T-shirts descended on Yuen Long’s metro station, beating protesters – as well as passersby and journalists – with wooden and metal sticks.
Forty-five people were injured in the attack, which was widely blamed on triad gang members.
Protesters said the police were slow to respond to emergency calls – and only appeared at the station after the attackers had left.
Police say their forces were stretched during another day of unrest, and said suggestions that they had colluded with criminal gangs was a “smear”.
Police say 12 people have so far been arrested over Sunday’s attack, including nine men with links to triads, reports say.