After Molotov cocktails were thrown the water cannon began firing the blue dye.
The outbreak of violence near Hong Kong’s parliament came after a peaceful march by tens of thousands of people earlier in the afternoon.
The mass act of civil disobedience came despite a ban on any protest and warnings that they would be arrested.
The protests followed efforts by Carrie Lam’s government to shut down pro-democracy voices ahead of the weekend through a series of arrests of activists and politicians.
Despite the ban hundreds of people gathered in Wanchai for what they said was a religious gathering at a playground around 1.30pm.
Police raised a yellow flag warning it was an illegal gathering before the people started to walk down Hennessy Road towards Government House.
Thousands of people across the generations marched up the hill to Government House shouting the chant of “Hong Kong Add Oil.”
By 3:30pm the protest numbers were growing as people marched to Chater Garden and then through Central past designer boutiques and banks.
There were no police visible in the city centre, but water cannon trucks had been parked near Beijing’s liaison office.
Joey, 39, said she originally planned to join the Civil Human Rights Front march but after it was banned heard from some Christians online that they would be walking to “pray for bad people”.
“I have found so many different kinds of people are coming along,” she said, her face uncovered and wearing no mask.
“I am singing Sing Hallelujah to the Lord – to express my prayers and also because I hope the police and the government will stop their evil to the citizens in Hong Kong.”
By 5pm tens-of-thousands of protesters marched towards government offices. In a provocative move, black clad protesters climbed a building to tear down a newly erected red banner celebrating the 70th anniversary of Communist China.
Just after 5.30pm, police began firing tear gas outside the Legislative Council.
As police ramped up pressure on Friday with a swathe of arrests, Civic Party’s Jeremy Tam, a former Cathay Pacific pilot, was taken into custody for obstructing police officers at a protest march last month.
Another Legislative Council member, Au Nok-hin, was arrested for shouting in a loudspeaker at a Mong Kok protest, and Cheng Chung-tai of Civic Passion was also detained by police.
The vice chairman of the Democratic Party, Lo Kin-hei, wrote on social media that opposition party legislators had gone to protest frontlines because they saw it was “carrying out their duty to monitor the use of force, and to minimise the conflicts between police and protesters”.
Politicians interviewed by The Sydney Morning Herald and The Age in July said it was “twisted” that after 2 million people had marched in the streets, neither Carrie Lam nor any of her cabinet ministers had resigned, as would occur in most democracies. It was therefore the duty of Hong Kong politicians “to ensure things don’t turn ugly” on the protest frontlines, they said.
The arrest of the prominent democracy voices, and the complete ban on a planned rally on Saturday, was viewed as an attempt to stop Hong Kong people coming out to the streets to mark the anniversary of Beijing refusing to grant universal suffrage for leadership elections.
Police warned that anyone attending the planned march on Saturday could be arrested, and also warned protesters against seeking legal loopholes for assemblies, such as religious gatherings which are exempt from public order laws.
Tourism officials at Hong Kong airport advised tourists to stay in their hotels on Saturday afternoon if they were on Hong Kong island.
The Hong Kong government appeared to be trying to undercut the pro-democracy movement in recent days.
Thomas, 55, said “Hong Kong police are triads.”
He said the arrests on Friday night were “nonsense”. “They just want to stop Hong Kong people.”
Young men in their twenties said they were “shopping”.
Earlier, on Saturday morning, the LIHKG forum used by protesters to organise their movements went out of action for several hours because of a large denial of service attack by hackers.
Water cannons were moved to Hong Kong island near the central liaison office.
On Friday high-profile Umbrella movement founders Agnes Chow and Joshua Wong were arrested and later released on bail.
Wong said it was “completely ridiculous” for police to target leaders from a previous social movement to frame them as leaders of the extradition bill protests.
State newspaper China Daily accused Hong Kong judges of siding with the protesters.
China Daily criticised the decision by a Hong Kong court to grant Wong and Chow bail, including allowing them to travel overseas on two pre-arranged trips.
A China Daily editorial on Saturday accused Hong Kong’s courts of handing light sentences to the leaders of the 2014 democracy protests in April.
“Hopefully the judges will do a better job of upholding the rule of law by staying apolitical this time,” the editorial said.
Many of the nine Occupy leaders were in fact jailed, but former university lecturer Benny Tai was released pending an appeal a fortnight ago.
Wong has also been released early after five weeks in jail in June, allowing him to join extradition bill protests.
Wong has urged the United States to change its designation of Hong Kong, impacting on trading relations, in light of the protests.
He and Chow were labelled “leading separatists” on the front page of China Daily.
This year’s protesters have described themselves as leaderless, and say they organise as a community through online platforms where ideas are voted up or down.
Pro-democracy politicians have also denied they are protest leaders.
Around two dozen pro-democracy politicians in the Legislative Council had been working tirelessly over the past three months to try to calm protesters and reason with police on protest frontlines, because they said they want to avoid violence.
Over 900 people have been arrested since protests began in June.
Kirsty Needham is China Correspondent for The Sydney Morning Herald and The Age.