Video appears to show police using long range pepper spray on a photojournalist who got too close to them.
Galileo Cheng told CNN he took the video while standing on Harcourt Road Flyover with his photographer friends.
“Basically, police first tried tear gas -- no use as Hong Kongers are used to it. Then they took out AR15 (rifles) and fired at people getting too close. I couldn’t tell the type of bullet but mostly rubber bullets or paint bullets. Bean bags is not used near PLA (Chinese People's Liberation Army Forces Hong Kong) headquarters. Crowd scattered now and gathered near Admiralty Centre side. I’m now at AIA tower near central. Situation is calmer now.”
6:06 a.m. ET, June 12, 2019
Protesters shelter in high-end mall
From CNN's Julia Hollingsworth
The glitzy, high-end Pacific Place mall is packed with young protestors, many wearing black shirts and face masks, and yelling in the usually quiet mall foyer.
Hundreds of protestors were driven back into the mall by the police's use of tear gas outside.
Now Pacific Place is packed with people, and there’s a sense of restlessness and frustration. Many have red eyes or faces from the gas outside, and groups are staying close to one another, trying not to lose each other in the tide of people.
Chi Chan, a 30-year-old office clerk, was one of the people pushed back from a walkway into Pacific Place. Sirens were ringing in the mall as she entered, set off by the gas outside.
Her boss let her leave work early to join the protest, and she arrived at 2.30 p.m., right before the gas began to fly.
She said she had come because was concerned by the Chinese legal systems’ lack of transparency, and said in the last five years Beijing had tried to influence Hong Kong too much.
Although Wednesday looked like it could be the beginning of another Umbrella movement, she said it would be more difficult for protestors to pull it off this time around -- the government and authorities had learnt from past experience.
“It’s not that easy,” she said.
6:27 a.m. ET, June 12, 2019
Police push protesters back along Harcourt Road
From CNN's Ben Westcott
The use of force by the Hong Kong police has succeeded in driving back protesters from Harcourt Road in front of the Legislative Council, the center of the unrest earlier in the day.
On Wednesday morning, this was the scene in the center of Harcourt Road.
By dusk, it was an altogether different image, as police fired tear gas and rubber bullets to push the crowds back, away from the government complex.
6:26 a.m. ET, June 12, 2019
Tear gas enters subway station
From CNN's Steve George
Images on social media appear to show panic in Hong Kong's Admiralty station as tear gas begins to drift into the subway, effecting passengers during the peak rush hour period.
The district where the protest is taking place is in the heart of the downtown area, close to the city's financial hub.
Police have cautioned residents to stay away from the protest area, but due to the relatively small size and compact nature of Hong Kong, this isn't always possible.
5:32 a.m. ET, June 12, 2019
Police face barrage from protesters
From CNN's James Griffiths
Protesters are seen throwing bits of debris at police as they try to come down the stairs of a walkway onto Harcourt Road.
5:09 a.m. ET, June 12, 2019
Footage shows tear gas being fired into the crowd
5:22 a.m. ET, June 12, 2019
Police use rubber bullets, bean bags, call protest a 'riot'
From CNN's Ben Westcott and Caroline Kwok
Commissioner of Hong Kong Police Steven Lo Wai-chung has confirmed that police have used a range of weapons -- including rubber bullets -- to suppress protests in the city center.
Alongside rubber bullets police have used tear gas, batons, pepper spray, pepper-spray solution and bean-bag rounds on Wednesday, Lo confirmed.
Lo defended the use of the heavy-duty emergency weapons by labelling the protest "a riot."
He said the protesters had attacked police lines and left officers with "no choice but to start to use force." He added that the pro-democracy protesters had used sharpened iron bars and bricks, resulting in injuries to a number of officers.
He urged residents not to enter the city's Admiralty area.
4:58 a.m. ET, June 12, 2019
Many protesters retreat into Hong Kong's malls
From CNN's Julia Hollingsworth and Ben Westcott
As the police continue to push back along Harcourt Road, many of the protesters have retreated into the nearby Pacific Place and Queensway shopping centers.
Police have used so much tear gas that it has set off the fire alarm inside the Queensway mall.
Even streets away, protesters are still able to feel the effects of the tear gas from around the Legislative Council.
The walkway above Harcourt Road, next to the government building, has now been cleared by police.
5:46 a.m. ET, June 12, 2019
Tear gas was a game changer in 2014. Will it be the same in 2019?
From CNN's Helen Regan and James Griffiths
It's the first time since the Umbrella Movement in 2014 that police have fired tear gas at protesters in Hong Kong.
Then, in the evening of September 28, police fired multiple rounds of tear gas at protesters, who had been gathering around the Legislative Council building all day.
The images of tear gas being used against young students galvanized the movement and the next day hundreds of thousands of people came out in support -- ultimately leading to the 79 day occupation of key areas in the city.
CNN's James Griffiths said: "Tear gas is what took Occupy from a student protest to a mass movement."
Read more about the return of Hong Kong's Umbrella Movement here.