Police fired water cannon and tear gas at Hong Kongers who defied authorities with an illegal march on Sunday, their numbers swollen by anger over the recent stabbing and beating of two pro-democracy protesters.
Authorities had forbidden the march in Tsim Sha Tsui, a densely packed shopping district filled with luxury boutiques and hotels, citing public safety and previous violence from hardcore protesters.
But tens of thousands joined the unsanctioned rally regardless, as the movement tries to keep up pressure on the city's pro-Beijing leaders after nearly five months of protests and political unrest.
In a now-familiar pattern, the rally began peacefully but quickly descended into chaos as small groups of hardcore protesters hurled petrol bombs at a police station, subway entrances and at Chinese mainland bank branches.
Hong Kong riot police discharge a blue water on protesters Source: EPA
Police responded with multiple volleys of tear gas.
At one point a water cannon truck chased thousands of protesters down Nathan Road, one of the city's busiest shopping thoroughfares, leaving it streaked with blue-dye from the vehicle's turrets.
The dye, used to identify protesters, also contains a pepper solution which burns the skin on contact.
As the protesters fled the streets, frontliners stayed behind to slow the advance of riot police, setting fire to makeshift barricades.
Tensions were already running high before the march was banned.
On Wednesday night the leader of the group organising the weekend rally, Jimmy Sham, was hospitalised by men wielding hammers.
A protester wearing a Guy Fawkes mask holds a flag during a rally in Hong Kong on Sunday Source: AAP
Then on Saturday night, a man handing out pro-democracy flyers was stabbed in the neck and stomach.
Footage posted on social media showed the alleged assailant shouting shortly after the knife attack: "Hong Kong is part of China... (You) messed up Hong Kong".
Figo Chan, from the Civil Human Rights Front - Mr Sham's group - said democracy supporters needed to show they remained unbowed.
"If we don't come out tomorrow, then violence will prevail and escalate: the violence inflicted by the regime, the police and local triads," Mr Chan told reporters Saturday.
Mob attacks
Vigilante violence has mounted on both sides of the ideological divide.
In recent weeks pro-democracy supporters have badly beaten people who vocally disagree with them - although those fights tend to be spontaneous outbursts of mob anger during protests.
In contrast, pro-democracy figures have been attacked in a noticeably more targeted way, with at least eight prominent government critics, including politicians, beaten by unknown assailants since mid-August.
Protesters carrying umbrellas march on a street in Hong Kong Source: AAP
Protesters have labelled the attacks "white terror" and accused the city's shadowy organised crime groups of forming an alliance with Beijing supporters.
Beijing has denounced the protests as a foreign-backed plot and condemned attacks on those voicing support for China.
But it has remained largely silent on the attacks carried out against pro-democracy figures.
Security was ramped up ahead of Sunday's march with key subway stations near the gathering shuttered early and a ring of steel thrown up around a nearby terminus for high-speed trains to mainland China.
Months of unrest
Hong Kong has been battered by 20 weeks of pro-democracy protests which have seen millions peacefully take to the streets.
But there have also been increasingly violent clashes between riot police and smaller groups of hardcore activists.
With no political solution in sight, the clashes have intensified each month.
Hardliners have embraced widespread vandalism and throwing petrol bombs, while riot police have responded with increasing volleys of tear gas, rubber bullets and, more recently, live rounds.
The rallies were triggered by a now-abandoned plan to allow extraditions to the authoritarian mainland. But they morphed into wider calls for democracy and police accountability after Beijing and local leaders took a hard line.
Protesters are demanding an independent inquiry into the police, an amnesty for those arrested and fully free elections, all of which have been rejected by Beijing and Hong Kong's leader Carrie Lam.
Earlier this month Ms Lam invoked a colonial-era emergency law to ban face masks.
The decision set off a new wave of protests and vandalism that shut down much of the city's transport network.
In the last fortnight, the clashes have become less intense with the city's subway closing each night at 10pm. But protests have continued with many defying the mask ban during "flashmob" rallies.
On Friday night thousands gathered outside subway stations in an array of face masks while on Saturday night hundreds of mostly masked protesters held a prayer vigil in the commercial district.
